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"D" SERIES BACKHOE LOADERS
INTRODUCTION
TECHNICAL PRESENTATION
Service TrainingMeeting Guide 746 SERV1746-01
October 2002
"D" SERIES BACKHOE LOADERSINTRODUCTION
MEETING GUIDE 746 SLIDES AND SCRIPT
AUDIENCE
Level II - Service personnel who understand the principles of machine systems operation, diagnosticequipment, and procedures for testing and adjusting.
CONTENT
This presentation discusses the design features, major components, and systems operation for the "D"Series Backhoe Loaders. Also included are descriptions of the operator's station and service points.
OBJECTIVES
After learning the information in this presentation, the serviceman will be able to:
1. locate and identify the major components in the operator's station, power train, and machinehydraulic systems including the optional All Wheel Steer system;
2. explain the function of the major components in the power train, machine hydraulic systems andthe optional All Wheel Steer system;
3. identify service points for the engine, power train, and machine hydraulic systems;4. trace oil flow through the transmission and machine hydraulic systems; and5. explain the operation of the starting and charging system.
PREREQUISITES
Interactive Video Course "Fundamentals of Mobile Hydraulics" TEMV9001STMG 546 "Graphic Fluid Power Symbols" SESV1546STMG 595 "Introduction to Load Sensing Pressure Compensated Hydraulic Systems" SESV1595STMG 630 "416B - 438B Backhoe Loaders - Steering and Implement Hydraulic Systems" SESV1677STMG 677 "416C - 438C Backhoe Loaders" SESV1677STMG 725 "416C - 438C Backhoe Loaders -Update" SESV1725Technical Instruction Module "Autoshift Transmission for Backhoe Loaders" SEGV2678
Estimated Time: 8 HoursVisuals: 104 (2 X 2) SlidesServiceman Handouts: 18 WorksheetsForm: SERV1746-01Date: 10/02
© 2002 Caterpillar Inc.
SUPPLEMENTARY TRAINING MATERIAL
STMG 629 "416B - 438B Backhoe Loaders–Introduction" SESV1629STMG 630 "416B - 438B Backhoe Loaders–Steering and Implement Hydraulic System" SESV1630STMG 604 "416 - 438 Series II Backhoe Loaders–Engine, Power Train and
Electrical Systems" SESV1604STMG 605 "416 - 438 Series II Backhoe Loaders–Steering and Implement
Hydraulic System" SESV1605
REFERENCES
Service Manual
416D Backhoe Loaders Service Manual RENR3570
Parts Manuals
416D Backhoe Loader BFP1-Up SEBP3202416D Backhoe Loader BGJ1-Up SEBP3236416D Backhoe Loader (G Version) BKG1-Up SEBP3241420D Backhoe Loader FDP1-Up SEBP3203420D Backhoe Loader BLN1-Up SEBP3204420D Backhoe Loader BKC1-Up SEBP3237420D Backhoe Loader BMC1-Up SEBP3238430D Backhoe Loader BNK1-Up SEBP3205430D Backhoe Loader BMC1-Up SEBP3206424D Backhoe Loader BGP1-Up, BKR1-Up SEBP3207428D Backhoe Loader BLL1-Up, BNB1-Up SEBP3208428D Backhoe Loader BMT1-Up, BNS1-Up SEBP3209438D Backhoe Loader BPE1-Up, BPN1-Up SEBP3211432D Backhoe Loader BLD1-Up SEBP3210442D Backhoe Loader BRG1-Up, BRY1-Up SEBP3212
Operation and Maintenance Manuals
416D Operation and Maintenance Guide SEBU7398420D/430D Operation and Maintenance Guide SEBU7399424D/428D/438D Operation and Maintenance Guide SEBU7400432D/442D Operation and Maintenance Guide SEBU7401
Specalogs
416D Specification Sheet AEHQ5419420D Specification Sheet AEHQ5420430D Specification Sheet AEHQ5421
STMG 746 - 3 -10/02
TABLE OF CONTENTS
INTRODUCTION .................................................................................................................5
ENGINE................................................................................................................................25Fuel System.....................................................................................................................27
ELECTRICAL SYSTEM .....................................................................................................34
POWER TRAIN ...................................................................................................................39Standard Transmission....................................................................................................39Autoshift Transmission ...................................................................................................44Axles and Brakes ............................................................................................................55
STEERING AND IMPLEMENT HYDRAULIC SYSTEMS..............................................62Steering and Implement Pump Operation.......................................................................74Loader Valve Groups and Steering System ....................................................................80Backhoe Valve Groups..................................................................................................110All Wheel Steer System (AWS)....................................................................................133
OPTIONAL MACHINE SECURITY SYSTEM (MMS) ..................................................134
CONCLUSION...................................................................................................................136
SLIDE LIST........................................................................................................................137
SERVICEMAN'S HANDOUTS.........................................................................................139
STMG 746 - 4 -10/02
1
• Center pivot models:
- Standard controls
- 416D
- Pilot controls
- 420D and 430D
• Sideshift models:
- Standard controls
- 424D
- 428D
- 438D
- Pilot controls
- 432D
- 442D
INTRODUCTION
The "D" Series Backhoe Loader Family is the latest generation ofCaterpillar Backhoe Loaders retaining many of the features proven on the"B and C" Series machines along with additional performance and designimprovements.
This presentation discusses the systems, major components, and featuresof the "D" Series Backhoe Loaders.
The "D" Series machines include the 416D, 420D and 430D which areequipped with the center pivot backhoe. The 420D and 430D featurepilot controlled implement hydraulics.
The "D" Series also includes the 424D, 428D and 438D sideshift modelswhich are popular in Europe. Additional sideshift models include the432D and 442D with pilot controlled implement hydraulics.
The new machine series features new paint themes to provide a bolderimage.
"D" SERIES BACKHOE LOADERS"D" SERIES BACKHOE LOADERS
INTRODUCTIONINTRODUCTION
© 2002 Caterpillar Inc.
2
• Similarities
SIMILARITIESWITH FORMER
MACHINES
• Engine• Thermal Starting Aid• Radial Seal Air Filters• Standard Transmission• Steering• Brake System• Hydraulic Pump• Mechanical Implement Controls• IT Linkage• All Wheel Drive
The "D" Series machines have many similarities to the machines they arereplacing.
The basic engine, standard transmission and steering systems are the sameas before.
The hydraulic brake system has multiple disc brakes and inboardplanetaries in the rear axle. The brake system is the same except for themaster cylinders being mounted differently than in the "C" Seriesmachines.
The hydraulic pump and controls are virtually the same as the "B" andlate production "C" Series, except for changes in operating pressures andflow rates.
Most of the daily service fill and check points can be accessed through thehinged engine hood.
3
• Differences
DIFFERENCESFROM
FORMERMACHINES
• Operator's Compartment
• HVAC
• Fuel Pump
• Starting and Charging System
• Autoshift Transmission
• Hydraulic Tank
• Reverse Signal System
• Stabilizer Valves
• Ride Control System
• High Rotation Buckets
• Pilot Controlled Hydraulics
The "D" Series machines feature several changes over the previousmodels to improve operator comfort and machine performance.
The operator compartment features new console layouts. The heating,ventilation and air conditioning components are located near the floor andprovide significant improvements to air circulation.
The fuel pump has been changed to the type also used on the 914G WheelLoader.
The electrical system has changed significantly from the previous models.Two fuse and relay blocks are located below a cover on the right sideconsole.
The autoshift transmission is the same as the power shift transmission onthe "C" Series except for the change in the software to convert toautoshift.
The hydraulic tank has been redesigned. A expansion tank is no longerrequired. A tube has also been added to make draining the tank mucheasier.
➥
The signal line routing has changed. With the reverse signal system, thelast resolver in the signal network is in the loader valve group instead ofthe backhoe valve group as per previous backhoe models.
Some machines are available with pilot operated controls for the backhoevalve group or for both the backhoe and the loader valve groups. Thepilot controls provide reduced lever efforts.
The stabilizer valves on all machines are pilot controlled and are differentin design from the previous versions.
Ride Control is similar in operation as before, however, the system designhas been modified.
Due to changes in the backhoe linkage, a single pin location is able toprovide improved performance for all backhoe operations. Previously,two pin positions were used.
• "D" Seriescomparison chart
4
This chart compares each "D" Series model to each other and reflectssome of the various options and features of each machine.
The 416D and 420D compete in the same size class and are replacementsfor the former 416C. The 416D is a lower cost version of the 420D andhas fewer available options. The 416D also has slightly lowerperformance ratings than the 416C, while the 420D has higherperformance ratings.
The 430D replaces the both the 426C and 436C in the marketplace.
The 420D and 430D feature pilot controls for the backhoe, while eithermechanical or pilot controls are used for the loader. Loader pilot controlsare only for machines with IT linkage.
416D 420D 430D 424D 428D 438D 432D 442D
CENTER PIVOT SIDE SHIFT
S SO S S S S S SS S S S S S S SS S S S S S S S
O O O O O OS S S S O
O O S S S SO O O O O O O OS S
S S S S S SS S S S S S S SS S
S S S S S SS S S S S SS S S S
O O O O S SS S S SO O O O O O
O O O O S S S SO O
O O O O O
S = Standard O = Option
3054 Naturally Aspirated Engine3054 Turbocharged Engine12-V Electrical SystemStandard TransmissionAutoshift Transmission (option)Single TiltIT LinkageRide ControlPump Flow 139 L/min (37 gal/min)Pump Flow 163 L/min (43 gal/min)Dynamic Bleed SteeringMaximum Pressure 20 685 kPa (3000 PSI)Maximum Pressure 22 754 kPa (3300 PSI)Mechanical Hydraulic Controls - LoaderMechanical Hydraulic Controls - BackhoePilot Hydraulic Controls - Loader (IT only)Pilot Hydraulic Controls - BackhoeAuto Up StabilizersAll Wheel Drive (AWD)All Wheel Steer (option)Machine Security System (option)
FEATURE DESCRIPTION
"D" SERIES BACKHOE LOADERS
➥
Additional comparisons can be made to the sideshift machines. The 424Dis the sideshift version of the 416D.
The 424D, 428D and 432D compete in the same size class. The 432D isequipped with pilot controls for both the loader and the backhoe. Theother two machines feature only mechanical controls.
The 438D and 442D compete in the next higher machine class. The 442Dis equipped with pilot controls.
The machine security system will only be available on the sideshiftmachines during the initial machine introduction. The center pivotmachines may have this as an option in the future.
All Wheel Steer (AWS) will not be made available on center pivotmachines until further notice.
5
• Cab features Several cab choices are available including an enclosed Roll OverProtection System (ROPS) cab as shown and and open ROPS.
The open canopy machines can be equipped with a air suspension vinylseat, tilt steering wheel, 12 Volt power supply, phone clip, a lockable leftside storage space, drink holders and floor mats.
On the 420D and 430D, the standard cab features an air suspension fabricseat, tilt steering wheel, 12 Volt power adapter, phone clip, a lockable leftside storage space, drink holders, floor mats, two doors, eight workinglights and opening rear windows. The machines are radio ready.
The deluxe cab has in addition to above, a nine-way adjustable airsuspension seat, auto-up stabilizer controls and additional systemmonitors. These monitors are for the voltmeter, fuel water separator,engine air cleaner and hydraulic filters.
The 416D is not available with the deluxe cab. The standard cab alsofeatures a single door which is on the left side of the machine. A cabupgrade is available with two doors and air conditioning.
NOTE: Sideshift machines have similar cab features as the centerpivot machines. Refer to the appropriate operation and maintenancemanual and specalogs for more information on all models.
6
• Machine controls:
1. Steering wheel
2. Transmissiondirectional selectorlever
3. Turn signal/wipercontrol lever
4. Four speedtransmission shiftlever
5. Loader controllever
6. Auxiliary controllever
7. Differential lock
8. Service brakepedals
9. Governor pedal
10. Parking brakelever
When sitting in the operator's seat and facing the front, various machinecontrols and features can be identified.
The cab shown is a machine equipped with mechanical loader controlslevers (5 and 6) to operate the front loader bucket with a single tiltcylinder.
The four speed transmission shifter (4) and directional selector (2) are formachines equipped with the standard transmission.
If the parking brake (10) is engaged when the operator selectsFORWARD or REVERSE, the fault alarm sounds.
1
23
4
56
7
8 9
10
STMG 746 - 13 -10/02
7
• Machine controls:
1. Autoshift speedand directionshuttle control
2. Loader joystick
3. Auxiliary buttons
4. Thumb switch
5. AWS positionindicator gauge
On machines equipped with a autoshift transmission, the speed rangeselector is part of the directional shuttle control (1).
Shown is the loader pilot joystick (2). The two yellow buttons (3) on thejoystick can be used to control an auxiliary function or for All WheelSteer (AWS). AWS will only be available on sideshift machines initially.
The thumb switch (4) provides input to the Auxiliary Control Module(ACM). The ACM directs a variable current to two proportionalsolenoids mounted on the loader auxiliary valve.
A switch (not shown) on the front of the joystick is used to downshift thetransmission or neutralize it depending on how long the switch is held.
In Autoshift Mode, if the switch is depressed for less than one second thetransmission downshifts. If the switch is held longer, the transmission isneutralized. In Manual Mode, the switch will not downshift thetransmission.
1
2
3
4
5
STMG 746 - 14 -10/02
8
• Left front console:
1. Alert indicatorpanel
2. AWD switch
3. Quick coupler pinswitch
4. Continuous flowswitch
5. Optionalwasher/sprayerswitch
6. TransmissionNEUTRAL lockswitch
The switches on the consoles will vary depending on how the machine isconfigured.
The alert indicator panel (1) includes: left and right turn signals, highbeams, parking brake and ride control.
The All Wheel Drive (AWD) switch (2) has three positions. One positionis for AWD OFF, another for AWD ON, and the other position for AWDON only when the brakes are applied. This last position allows for bettermachine braking by locking up the entire driveline. In affect, all fourwheels are used to brake the machine even though the front wheels arenot equipped with brakes.
A quick coupler pin switch (3) is used on machines equipped with theIntegrated Toolcarrier (IT) style dual tilt cylinder bucket and parallel liftarms. The switch is used to release or lock the coupler pins from anattachment.
➥
1
2
3
4
5
6
STMG 746 - 15 -10/02
The continuous flow switch (4), is an option that works with theproportional solenoid controlled loader auxiliary circuit. The switch ismomentary. After the desired flow rate is selected with the loaderjoystick thumb switch. Press and release the continuous flow switch.Then release the thumb switch. The feature is used with brooms or otherattachments where continuous flow is required.
The optional washer/sprayer switch (5) is used to control a separatefunction such as a washer for a broom.
The transmission NEUTRAL lock switch (6) prevents the transmissionfrom being shifted into a direction. The directional selector lever can bemoved, but the transmission will not shift until the lock switch is turnedoff.
STMG 746 - 16 -10/02
9
• Right front console:
1. Flasher
2. Autoshift switch
3. Ride Controlswitch
4. COSA roading lightswitch location
5. Horn
The autoshift switch (2) allows the operator to switch between Manual orAutoshift Modes. In autoshift, after the operator selects the maximumspeed range on the shift selector lever, the machine automatically shiftsthe machine based on ground speed. Maxium speed gear in autoshift isfifth, while manual is limited to fourth. The shift lever only shows up tofourth gear; however, in autoshift the transmission will shift into fifth gearbased on ground speed.
The Ride Control switch (3) is used to select the different modes ofoperation. The optional Ride Control system provides a smoother ridewhen the machine is driven over rough terrain. On machines equippedwith autoshift, the transmission ECM monitors the position of the RideControl switch and determines when to operate the Ride Control system.
If the machine is equipped with AWS, a gauge and switches to select theAWS mode are also mounted on the right front console (not shown).(AWS will discussed later in this presentation.)
1
2
3 4
5
STMG 746 - 17 -10/02
10
• Loader controls:
1. Pilot joystick
2. Alert indicators
3. Key start switch
4. Hydraulic lockswitch
5. Governor lever
6. Boom lock lever
7. Stabilizer pilotcontrol levers
The loader controls are located in the side console.
The side console is equipped with additional gauges, switches andcontrols.
The alert indicators (2) include: engine oil pressure, coolant level,charging and brake level.
The additional switches and controls on the side of the console vary withmachine configuration. Gauges include: tachometer, fuel level, coolanttemperature and power train temperature.
The key start switch (3) no longer has an accessory position as did the "C" Series machines.
The hydraulic lock switch (4) controls a pilot shutoff solenoid valve onmachines with pilot controls. The switch energizes the pilot shutoffsolenoid when the key start switch is turned ON to allow pilot oil to thejoysticks to operate the implements.
When the key start switch is turned OFF or the switch is moved to theLOCK position, the joysticks are disabled.
➥
1
2
3
4
5 6
7
STMG 746 - 18 -10/02
With mechanical controls, the hydraulic lock switch controls an optionalhydraulic shutoff solenoid valve instead. When the hydraulic lock switchis moved to the LOCK position, the valve is energized and blocks supplyoil to the backhoe valve group when roading the machine.
The rear governor lever (5), boom lock lever (6), and stabilizer pilotcontrol levers (7) are also located in the side console.
The action alarm (if equipped) will sound when one or both stabilizers areraised if the transmission direction control lever is shifted fromNEUTRAL.
The stabilizer control system may feature auto-up, which holds the leversin detent for a set time to automatically raise the cylinders. The timer cannot be adjusted.
STMG 746 - 19 -10/02
11
• Mechanical backhoecontrols:
1. Swing and boom
2. Stick and bucket
3. Boom lock lever
When the operator is facing the rear of a machine on, the standardbackhoe controls can be identified.
The standard control pattern for the "D" Series is the same as on allprevious backhoe models. The long lever on the right (2) is used tocontrol bucket and stick. The long lever on the left (1) is used to controlthe boom and swing.
The boom lock lever (3) has been moved to the side console.
A pedal or pedals (not shown) on the floor are used to control theauxiliary functions like the E-stick or a hammer.
To satisfy the needs of the customer, optional control configurations areavailable.
1 2
3
STMG 746 - 20 -10/02
12
• Pilot operatedbackhoe:
1. Stick and swing
2. Bucket and boom
3. Pods
4. Pilot control podlever
5. Swing lock pin
6. E-stick pedal
The backhoe controls for machines equipped with pilot controls areshown.
The pilot control pattern for the "D" Series is the same as the Catexcavator pattern. The joystick on the right (2) is used to control bucketand boom. The joystick on the left (1) is used to control the stick andswing. A switch to activate the horn is part of the left joystick.
The joysticks are mounted to pods (3).
The pilot control pod lever (4), locks the joystick pods until the operatorreleases the pods in order to move the joysticks for and aft to anergonomically correct position.
E-stick pedal (6) is used to control an auxiliary valve through mechanicallinkage. On some machines an additional pedal (not shown) can be usedfor an additional auxiliary function.
To satisfy the needs of the customer, optional control configurations areavailable including the Cat backhoe pattern.
1 2
34
5
36
STMG 746 - 21 -10/02
13
• Pattern changer valvelever:
1. Lever
2. Hole
An optional feature on machines with joystick controls is a patternchanger valve (not shown) mounted to the inside of the frame on the leftside of the machine.
The lever (1) is in position #1 for the excavator control pattern.
The lever can be moved to a different position to change from excavatorto a backhoe control pattern.
To select the backhoe control pattern the bolt must be removed from theend of lever. The lever can then be rotated to the lower hole (2) forposition #2.
The bolt is then reinstalled in the hole to hold the lever.
The #1 and #2 are stamped into the frame.
1
2
STMG 746 - 22 -10/02
14
• "D" Series buckets:
- Bucket stop plates
The "D" Series backhoes feature "high rotation" backhoe linkage. Asingle pin bucket position contributes to 205 degrees of rotation. This issuitable for all applications eliminating the need to change pin positionsas was done on all previous backhoes.
An integral lifting eye (not shown) is a standard feature of the bucketlinkage.
Bucket stop plates (arrows) allow "C" Series buckets to be used on "D"Series machines. When a "C" Series bucket is attached, the plates mustbe moved to the other side of the linkage to limit "C" Series bucket travel.
Without the stops, the "C" Series buckets will contact the stick.
STMG 746 - 23 -10/02
15
• Service points:
1. Air filter housing
2. Engine oil fill tube
3. Engine dipstick
4. Hydraulic tank filltube
5. Transmission filltube
6. Air filter indicator
7. Washer fill bottle
8. Brake reservoir
Most daily service fill and check points are located below the hingedhood.
Radial seal air filters are used on these machines.
12
3
4 5
6
7
8
STMG 746 - 24 -10/02
16
• Hydraulic sight gauge(arrow)
The hydraulic sight gauge (arrow) is located on the left side of themachine in front of the cab on the loader tower.
STMG 746 - 25 -10/02
17
• Service points andcomponents:
1. Radiator fill cap
2. Power train andimplementhydraulic systemoil cooler
3. Condenser
4. Compressor
5. Fuel filter
6. Fuel pump
7. Fuel fill tube
8. Fuel tank drainplug
9. Decal
ENGINE
The "D" Series backhoe loaders are powered by direct injection, fourcylinder, Caterpillar 3054T diesel engines. Most of the models areturbocharged. The 3054B naturally aspirated engines for the 416D and424D use similar components, but are not equipped with an engine oilcooler.
The 3054B is the specific model designation for the 103 mm bore engine.to meets EPA Tier 1 emissions. The increased bore size gives it a totaldisplacement of 4.43 liters. All other 3054 engines have 4.0 literdisplacement. One other significant difference is that the 3054B islinerless. All other 3054's are built with dry, replaceable liners.
In front of the radiator is a combination power train and implementhydraulic system oil cooler (2). The two systems are separate, but use acommon cooler assembly.
If the machine is equipped with air conditioning, the condenser (3) ismounted at the front of the engine compartment. The air dryer (notshown) is located behind the rear axle.
The decal (9), identifies the access point behind the frame to drain thefuel/water separator.
1
2
3
4
5
6
7
8
9
STMG 746 - 26 -10/02
18
• Engine compartmentcomponents:
1. Thermal startingaid
2. Fuel lift (priming)pump
3. Starter
4. Alternator
5. Radiator
Shown here are the components on the right side of the enginecompartment.
The standard alternator (4) is rated for 55 amps. An optional 90 ampalternator is also available.
The cooling system features an automotive-type radiator (5).
NOTE: The thermal starting aid was called the start aid coil on "C"Series machines.
1
2
3
4
5
STMG 746 - 27 -10/02
• Fuel flow through fuelsystem:
- Water separator/fuelfilter
- Lift pump
- Fuel filter
- Distributor-type fuelinjection pump
- Injectors
- Return to tank
19
SCROLL PLATES
BOOSTPRESSURE
BOOSTCONTROLLER
FUEL TANK
FEEDPUMP
MAINFILTER
TRANSFERPRESSURE
REGULATOR
VENT ORIFICEFUEL RETURNCHECK VALVE
ORIFICECHECK VALVE
LIGHT LOADADVANCE VALVE LATCH
VALVE
COLD ADVANCEDEVICE
TRANSFERPUMP
SHUTOFFSOLENOID
METERINGVALVE
INJECTORTORQUETRIMMER
ROTORCAMRING
ROLLERS
PLUNGERS
WATERSEPARATOR
DELIVERYVALVE
AUTOMATICADVANCE
MECHANISM
FUEL HYDRAULIC SYSTEMENGINE RUNNING
HYDRAULICHEAD
FLATSHOES
Fuel System
All components shown in the schematic except for the fuel tank, waterseparator/fuel filter, lift pump, fuel filter and injector are part of the fuelinjection pump.
The feed or lift pump is used to move fuel from the fuel tank to a higherlevel on the machine. The pump is also used to prime the system.
The water separator removes water from the fuel. Since the fuelinjection pump is lubricated by fuel, it is extremely important that waterdoes not enter the pump. Water will cause the pump to malfunction andwill lead to the rotor and plungers locking up. The water separator shouldbe serviced daily.
➥
STMG 746 - 28 -10/02
The transfer pump draws fuel from the tank and supplies fuel to theinjection pump.
The hydraulic head is machined with bores and passages which allowfuel to flow to and from a specific point. For example, fuel flows fromthe transfer pump to the metering valve or from the metering valve to theinlet passage to the rotor.
The rotor is located in the hydraulic head. The rotor distributes fuel tothe delivery valves. The rotor has four inlet passages and one outletpassage. As the rotor turns, fuel enters the passages in the rotor andforces the plungers in the drive end of the rotor outward. As the rotorcontinues to turn, the inlet passage closes. As the plungers are forcedinward by the cam ring and rollers, the fuel pressure in the rotor increases.At the same time, the outlet passage opens and fuel exits the rotor throughthe delivery valves to the injectors.
The transfer pressure regulator controls the fuel transfer pressurewithin the injection pump. Transfer pressure will increase as enginespeed increases. The regulator also permits the fuel to bypass the transferpump when the fuel system is being primed.
The shutoff solenoid allows fuel to enter the fuel injection pump whenthe solenoid is energized. When the key start switch is moved to the OFFposition, the solenoid is de-energized and a spring moves the plunger inthe solenoid to block fuel flow.
The metering valve controls the amount of fuel to the hydraulic head orrotor. The valve is connected to a mechanical governor and the throttle orgovernor control lever. As the metering valve is rotated within thehydraulic head, a delivery control groove in the valve precisely metersfuel to the rotor.
A tapered flat on the metering valve works with the light load valve. Theflat is machined in line with the delivery control groove.
➥
STMG 746 - 29 -10/02
The light load advance valve and metering valve work with two controlorifices in the hydraulic head to override the normal speed advancesystem. During low load conditions, the outward travel of the rollers andshoes is reduced during the rotor filling cycle, which delays the point ofroller contact with the cam lobes resulting in retarded injection.
The light load advance compensates for this delay by advancing injectionat reduced fuel levels. Passageways are drilled within the hydraulic headbody to connect the metering valve "flat" with the pressure end of theadvance device (through a second control orifice) and the pump cambox.
As the metering valve is rotated in the hydraulic head by the governor, alarger or smaller flow path from the advance piston to the cambox iscreated. The relationship between the "flat" with the delivery controlgroove is arranged so that, as delivery is reduced, flow past the flat is alsoreduced. Thus, the pressure signal applied to the advance piston isincreased to advance the timing.
The boost controller adjusts the maximum fuel delivery based onvariations in the boost pressure from the turbocharger. As boost pressureincreases, the scroll plates rotate and allow the plunger travel to increase.This action permits an increase in fuel delivery resulting in more enginehorsepower.
The torque trimmer provides a means to regulate the volume of fuelbeing delivered at full load. The torque trimmer provides the maximumamount of fuel in the loadable range of the engine which can be burnedsmoke free.
The delivery valves are check valves which open to allow fuel from thepumping mechanism to the injectors. There is one delivery valve perinjector. The valves rapidly reduce pressure in the injector lines at the endof the injection cycle to ensure a rapid closure of the injector nozzles and,in conjunction with the cam ring profile, maintain a residual pressure inthe fuel lines to the injectors.
The latch valve prevents transfer pressure from reaching the automaticadvance mechanism during cranking until the engine is started to preventpremature advance timing.
➥
STMG 746 - 30 -10/02
The automatic advance mechanism progressively advances the start ofinjection as engine speed increases. The automatic advance mechanismcauses the cam ring to rotate in the pump housing. The spring in themechanism moves the piston and cam ring to retard the timing, whiletransfer pressure sensed on the left side of the piston works against thespring to advance the timing.
The check valve prevents reverse fuel flow from the automatic advancedue to cam loading. The orifice permits fuel to vent from the automaticadvance when the engine rpm are reduced.
The cold advance device is used to reduce white smoke by advancing theengine timing to improve cold idling combustion capability. The coldadvance device is sometimes called a "wax motor" and is a relatively slowresponse actuator.
At start-up, a check valve prevents transfer pressure from flowing to theright end of the automatic advance mechanism preventing the sleeve frommoving away from the start advance position. This action prevents thespring from fully retarding the engine timing. After the engine is startedand allowed to warm up to a specified temperature, a coolant switchcloses and current is sent to the wax motor causing the wax to melt.
As the wax melts, it changes in volume and goes from a solid to a liquid.After approximately 25 seconds or more, the pin in the device moves tothe left and unseats the check valve. Transfer pressure then flows to theright end of the automatic advance mechanism and moves the sleeve tothe left against a stop to the normal automatic advance operating mode.
The fuel return check valve maintains a slight pressure in the fuelinjection pump to ensure good lubrication. The fuel return check valvealso allows hot fuel to bleed from the injection pump for cooling.
NOTE: Only the 430D, 438D and 442D backhoe loaders areequipped with a boost controller.
➥
STMG 746 - 31 -10/02
The various color codes which are used in this presentation to identifyoil flow and pressures for the fuel hydraulic system are as follows:
Pink - Reduced transfer pressure
Red Dots - Transfer pressure
Red - High pressure fuel
Blue - Blocked fuel
Green - Suction or drain fuel
Purple - Boost air pressure
STMG 746 - 32 -10/02
• Fuel injection pump
20
This illustration shows a sectional view of the fuel injection pump.
Fuel is drawn by the transfer pump through the pressure regulator and sentto the metering valve when the solenoid is energized. The fuel also flowsthrough an annular groove around the rotor to the orifice check valve andthe automatic advance mechanism.
The metering valve controls the amount of fuel sent to the pumpingelements inside the rotor (plungers, cam ring and shoes). As the rotorturns, the cam ring forces the shoes and plungers in to increase the fuelpressure. The pressurized fuel is then directed to the injectors.
THROTTLE LEVER
FUEL SHUTOFFSOLENOID
FUEL RETURNCHECK VALVE
VENT ORIFICE
DRIVESHAFT
LOW IDLESTOP
HIGH IDLESTOP
GOVERNORSPRING
SHIFTER ANDSLEEVE
GOVERNORFLYWEIGHTS
AUTOMATIC ADVANCEMECHANISM
ORIFICECHECK VALVE
TO INJECTOR
CAM RINGROLLERS
SHOES
PLUNGERS
SCROLL PLATES
METERING VALVE
TRANSFERPUMP
TRANSFERPRESSURE
REGULATOR
FUEL INLET
SCREEN
FUEL INJECTION PUMP
SCROLL LINKPLATE
STMG 746 - 33 -10/02
21
• Fuel injection pumpcomponents:
1. Boost controller
2. Fuel shutoffsolenoid
3. Fuel transferpressure regulatorand inlet
4. Torque trimmer
5. Latch valve
6. Locking bolt
7. Automatic advancemechanism andcold advancedevice
8. Delivery valve
• Additional enginecomponent:
9. Oil pressure switch
The fuel injection pump is locate on the left side of the engine. Only the430D, 438D and 442D are equipped with a boost controller (1).
If a new pump is installed on the engine, a locking bolt (6) and a twoposition spacer in the pump flange below the timing mark on the pumpengine flange must be loosened after installing the pump on the engine.In the locked position, the bolt prevents the pump drive shaft fromturning. Move the spacer to provide additional clearance between the bolthead and the pump flange to unlock the pump drive shaft.
If this procedure is not performed, the fuel pump will be damaged if anattempt is made to start the engine. If the timing pin was used this boltmay not have been used to prevent the pump drive shaft from turning.
The oil pressure switch (9) can be removed to install a test nipple to checkengine oil pressure.
NOTE: Refer to service manual module "Lucas Fuel PumpSupplement" (Form SENR6525) for more information on removingand installing the fuel injection pump.
This is the same type of fuel pump used on the 914G and IT14G.
12
34
5
6
7
8
9
STMG 746 - 34 -10/02
• Starting systemoperation:
- Batteries
- Key start switch toSTART-RUN
- Energize shutdownsolenoid
- Transmission shuttlecontrol in NEUTRAL
- Start relay closes
- Energizes startersolenoid
- Turns starter motor
22
ELECTRICAL SYSTEM
This schematic shows the 12-Volt electrical starting and charging systemwith the key start switch in the RUN position. From the batteries, powerflows to the battery post on the starter, to the fuse relay blocks. FromFuse Relay Block 1, power flows to the key start switch.
When the key is in the START-RUN position and the transmission shiftcontrol lever is in NEUTRAL, the start relay is energized through thetransmission shuttle control (shift lever). With the start relay closed,power from the battery energizes the starter solenoid and motor. Thestarter then engages the flywheel ring gear and starts the engine. If thetransmission shuttle control is not in NEUTRAL, no power is directed tothe start relay, so the engine will not crank.
TO FUSES
CABRELAY
327-PK
327-PKFUEL
SHUTDOWNSOLENOID
T°
334 BU COLD STARTADVANCESOLENOID
COLD STARTTEMP. SW.
310-PU
STARTAID SW.
THERMALSTARTING
AID
STARTRELAY
306-GN
202-BK
SHUTTLECONTROL
123456789
101112
BATTERYGROUND
FORWARD SOL RETURNREVERSE SOL RETURN
FORWARD SOL. OUTREVERSE SOL. OUT
START RELAY COIL OUTKEY START SW. TO BAT
NEUTRALIZER SW. TO BATPARK BRAKE ALARM OUT
PARK BRAKE SW. TO GND.NEUTRAL LOCK SW. TO GND.
CBL RD-00
5 A
POS NEGPOS NEG
G S
MOTOR
MTR BAT
STARTER
105-RD
307-OR304-WH
101-RD
MAINRELAY
ATTACHMENTRELAY
KEY STARTSWITCH
101-RD
R
CSB ST
OFF
ON
308-YL
450-YL
ALTERNATOR
TACH.
309-GY
ACTION LAMPGROUP
KEY START
ALT
B+
1 2 3L IG P
15 A
131-RD
AC
AC
TO HVAC RELAY
TO RR LIGHTING RELAY
TO FUSES
TO FUSES
10AENGINE FUEL
20A
THERMAL STARTAID
1234
AB
12
101-RD
AC
AC
TO FUSES
TO FRONTLIGHTING RELAY
START RELAY
10ATRANSMISSION
123-WH
"D" SERIES STARTING AND CHARGING SYSTEMEMISSIONS ENGINE / RUN
338-PK
338-PK
FUSE RELAY BLOCK 1
FUSE RELAY BLOCK 2
➥
STMG 746 - 35 -10/02
When the key is in either the START or RUN position, the fuel shutoffsolenoid is energized and allows fuel to flow through the fuel injectionpump. Thus, the solenoid is "energized to run."
Turning the key start switch to the OFF position de-energizes the engineshutdown solenoid. The solenoid moves the metering valve linkage to the"fuel off" position.
For cold starts, the start aid switch can be used to energize the thermalstarting aid while cranking the engine. When the start aid switch isclosed, power to the thermal starting aid heats the coil. Expansion withinthe coil assembly permits fuel to flow through a check valve when theengine is cranked. The heated fuel becomes a vapor and, as it flows pastthe coil into the inlet manifold, the fuel is ignited. The ignited fuel heatsthe inlet air.
When the key start switch is turned to the RUN position or the start aidswitch is released, the inlet air cools the coil assembly quickly. The checkvalve closes and blocks the fuel supply line.
The battery is charged by a belt-driven alternator. The alternator is notself-energizing and requires battery voltage to start up.
When the key start switch is in the RUN position, power from the batterygoes through the switch to the "IG" terminal of the alternator to excite thealternator field.
With the key start switch in the RUN position, the main relay is closedand power is directed to the accessories and additional relays.
The cold start advance solenoid does not energize until the cold starttemperature switch closes.
• Key start switch inSTART or RUN:
- Fuel shutoffsolenoid energized
• Key start switch toOFF:
- Fuel shutoffsolenoid de-energized
• Charging systemoperation:
- Key start in RUN
- Small currentexcites alternator
- Alternator chargesbatteries and powersaccessories
- Main relayclosed–power toaccessories andother relays
STMG 746 - 36 -10/02
23
• Electrical system:
- 12-Volt system
- One battery isstandard
- No disconnectswitch
The "D" Series backhoe loaders are equipped with conventional 12-Voltelectrical systems with negative ground.
The standard machines are equipped with a 12-Volt maintenance freebattery to supply power to the system. The machines can be equippedwith two batteries along with a heavy duty alternator for cold weatherclimates or for use with additional operating lights (attachments).
The system does not have a disconnect switch. To disable the electricalsystem, remove the battery ground cable from the main frame. Thestarting system is a key start and stop system.
The Autoshift ECM (1) for a machine equipped with an autoshifttransmission is also located in the battery compartment.
The diagnostic indicator lamp (2) is used to access active faultinformation from the control module. The indicator flashes 2-digit faultcodes.
The harness connector is a two-pin plug DT connector (3) with an end-termination receptacle.
• Autoshifttransmission:
1. Autoshift ECM
2. Diagnosticindicator lamp
3. DT connector
➥
1
2
3
STMG 746 - 37 -10/02
During normal operation this plug is installed in the connector. "If asystem problem is detected by the transmission control, the diagnosticindicator will turn on and remain on as long as the problem is active."Turning "on" means the diagnostic indicator will cycle through all flashcodes present.
Removing the termination plug from the connector will cause the lamp toflash the first active (low number to high number) two digit fault thetransmission control finds. The problem is displayed by blinking thediagnostic indicator. A valid diagnostic code will consist of a series ofblinks, (which is the first digit), followed by a short pause, and then asecond series of blinks (which is the second digit). If no active problemsare present, the control will broadcast diagnostic code "11".
NOTE: Also, located in the battery compartment, but not shown, is abolt used to manually lower the pilot controlled implements. The boltprovides dead engine lowering capabilities. The bolt should only beused for lowering the loader end and not the backhoe, due to safetyconcerns.
STMG 746 - 38 -10/02
24
• Electricalcomponents:
1. Fuse and relayblock 1
2. Fuse and relayblock 2
3. Diagnosticconnector
The fuse and relay blocks (1 and 2) are located below covers on the rightside of the cab. The diagnostic connector (3) to connect ElectronicTechnician (ET) is also shown.
Additional relays (not shown) are located in the side console. Access tothese relays is obtained by moving the gauge and switch panel in the sideconsole shown earlier.
1
2
3
STMG 746 - 39 -10/02
• Standardtransmission:
- Four-speeds
- Directional clutchescontrolled bysolenoids
25
POWER TRAIN
Standard Transmission
The standard countershaft transmission is the same as the "C" Seriestransmission.
The four-speed, direct drive, helical gear, constant mesh, synchronizedstandard transmission is coupled with hydraulically engaged FORWARDand REVERSE clutches. Each multiple disc clutch pack is controlled bya solenoid valve.
A manually actuated lever and shifter fork arrangement shifts thetransmission through the four fully synchronized speed ranges.
IDLERSHAFT
PUMP
INPUTSHAFT
TORQUECONVERTER
HOUSING
COUNTERSHAFT
OUTPUTSHAFT
AWDSHAFT
FORWARDCLUTCH
REVERSECLUTCH
SPEED GEAR
SYNCHRONIZERASSEMBLY
AWDCLUTCH
STANDARDBACKHOE LOADER
TRANSMISSION
➥
STMG 746 - 40 -10/02
• AWD:
- Solenoid controlledclutch
- Switch on frontconsole
Power is transmitted from the torque converter to the input shaft. IfFORWARD is selected, the FORWARD clutch is engaged and powerflows from input shaft to the countershaft. The countershaft causes allfour speed gears to rotate. A synchronizer will engage one of the speedgears with the output shaft. Power is then directed to the rear axle.
If the machine is equipped with All Wheel Drive (AWD), a separate shaftand clutch are needed. An additional gear on the output shaft willtransmit power to the AWD shaft.
A multiple disc clutch is part of the AWD shaft group. The clutch ishydraulically engaged and spring released. A solenoid controlled valve(not shown) directs oil to pressurize or drain the clutch. The solenoid isconnected to a switch on the front console (shown earlier). The frontwheel drive axle can be engaged while the vehicle is moving by operatingthe switch.
INSTRUCTOR NOTE: The various color codes which will be usedin this presentation to identify oil flow and pressures for the powertrain hydraulic system are as follows:
Red - Pump supply or directional clutchpressure
Orange - Torque converter inlet pressure
Brown - Lube oil
Green - Suction or drain oil
STMG 746 - 41 -10/02
• Two Wheel Drivecomponents:
- Suction screen
- Pump
- Oil filter
- Directional selectorsolenoid valve
- Relief valve
- Torque converterinlet relief valve
- Cooler
- Lube circuit
26
This illustration shows the power train hydraulic schematic for thestandard transmission equipped with Two Wheel Drive.
Oil from the sump is drawn though a suction screen by a crescent-typegear pump located on the transmission input shaft. From the pump, the oilis sent through a spin-on filter to the transmission directional selectorsolenoid valve.
In NEUTRAL, the oil flow is blocked by the directional selector solenoidvalve. Therefore, the oil opens the relief valve and flows to the torqueconverter. A bypass orifice in the relief valve, is located between thesupply circuit and torque converter circuit to make sure that oil is alwaysavailable to the torque converter when the machine is running.
TORQUECONVERTER
LUBE
TORQUECONVERTER
OUTLETOIL COOLER
TRANSMISSIONLUBE
SUCTION SCREEN
PUMP
FILTER
R
F
DIRECTIONAL SELECTORSOLENOID VALVE
TORQUECONVERTERINLET RELIEF
VALVE
RELIEFVALVE
PUMPSUPPLY
TORQUECONVERTER
INLET
STANDARD POWER TRAINHYDRAULIC SYSTEM
NEUTRAL
➥
STMG 746 - 42 -10/02
The torque converter inlet relief valve protects the automotive-type torqueconverter from high pressure (during cold start-up). Oil from the torqueconverter goes to the oil cooler, which is located in front of the radiator.
From the cooler, the oil is used for lubrication. A passage directs lube oilto the input shaft of the transmission. Oil from the shaft cools andlubricates the clutch assembly and input shaft bearings. The output shaft,countershaft and reverse idler shaft are splash lubricated. The oil thenreturns to the sump.
NOTE: The lines and fittings from the torque converter and the oilcooler are sized to provide sufficient restriction to the oil in the torqueconverter. A torque converter outlet relief valve is not required.
The cold start relief valve between the pump and filter on the "C"Series has been removed on the "D" Series. The valve is no longerrequired.
STMG 746 - 43 -10/02
• AWD components:
- AWD solenoid andclutch
27
This illustration shows the power train hydraulic schematic for thestandard transmission equipped with All Wheel Drive (AWD).
The power train hydraulic system for AWD machines is the same as thetwo wheel drive machines except for an external supply line which directssupply oil to the AWD solenoid valve. When the solenoid is energized,oil engages the AWD clutch.
This schematic shows that the directional selector solenoid valve has beenenergized. Supply oil flows through the valve to engage the FORWARDclutch. The relief valve limits the maximum clutch pressure.
TORQUECONVERTER
LUBE
TORQUECONVERTER
OUTLETOIL COOLER
TRANSMISSIONLUBE
SUCTION SCREEN
PUMP
STANDARD POWER TRAINHYDRAULIC SYSTEMALL WHEEL DRIVE / FORWARD
FILTER
AWD
R
F
DIRECTIONAL SELECTORSOLENOID VALVE
TORQUECONVERTERINLET RELIEF
VALVE
AWD SOLENOIDVALVE
RELIEFVALVE
PUMPSUPPLY
TORQUECONVERTER
INLET
STMG 746 - 44 -10/02
28
• Autoshifttransmission:
- Five-speeds forward,three-speedsreversetransmission
- Three speedsolenoids
- Three directionalsolenoids
INPUTSHAFT
OUTPUTSHAFT
AUTOSHIFT TRANSMISSION
PUMP
SOLENOIDVALVES
AWDSHAFT
COUNTERSHAFT
Autoshift Transmission
A torque converter (not shown) provides a fluid connection between theengine and the transmission.
The five-speeds forward, three-speeds reverse, autoshift transmission is aconstant-mesh, countershaft design. The transmission transfers power tothe drive axles. The Autoshift ECM electronically controls thetransmission by selectively energizing speed and directional solenoids.The transmission is equipped with three speed and three directionalsolenoids. One speed solenoid and one directional solenoid must besimultaneously energized for a transmission gear to be engaged.
Transmissions with the optional AWD system are equipped with an AWDsolenoid and an additional output shaft.
NOTE: The reverse shaft and clutch are not shown in this sectionalview. It is shown later in this presentation.
STMG 746 - 45 -10/02
29
• Autoshift power trainhydraulic system inNEUTRAL
• Components:
- Suction screen
- Pump
- Oil filter
- Solenoid valve
- Relief valve
- Torque converterinlet relief valve
- Oil cooler andbypass
- Lube circuit
- ECM
3
2
REGULATEDPRESSURE
1
LUBE
TORQUECONVERTER
OUTLET
TRANSMISSIONLUBE
SUCTIONSCREEN
LO
HI
OIL COOLER
RFORWARD
AUTOSHIFT POWER TRAINHYDRAULIC SYSTEM
NEUTRAL
6
ORIFICE
SOLENOIDVALVE
5 1 3 4
AUTO/MANUAL SWITCHNEUTRAL LOCK SWITCH
RIDE CONTROL SWITCH
PARKING BRAKE SWITCH
DOWNSHIFT/NEUTRALIZER SWITCH
RIDE CONTROL DISABLE
2
DATA LINKSERVICE PORT
SHIFT LEVER
TRANSMISSION OUTPUT SPEED SENSOR
FILTER
PUMP TORQUECONVERTER
TORQUECONVERTER
INLETRELIEF VALVE
RELIEFVALVE
AUTOSHIFTECM
TORQUECONVERTER INLET
PUMPSUPPLY
This illustration shows the power train hydraulic schematic for theautoshift transmission equipped with Two Wheel Drive.
Oil from the sump is drawn though a suction screen by a crescent-typegear pump located on the transmission input shaft. From the pump, the oilis sent through a spin-on filter to the transmission solenoid valves.
In NEUTRAL, the oil flow is blocked by the solenoid valves. The supplyoil opens the relief valve and flows to the torque converter. A bypassorifice in the relief valve is located between the supply circuit and torqueconverter circuit to make sure that oil is always available to the torqueconverter when the machine is running.
➥
STMG 746 - 46 -10/02
The torque converter inlet relief valve protects the automotive-type torqueconverter from high pressure (during cold start-ups). Oil from the torqueconverter goes to the oil cooler, which is located in front of the radiator.An oil cooler bypass valve is used to protect the cooler from excessivepressure caused by cold oil.
From the cooler, the oil is sent to the transmission circuit. A passagedirects lube oil to the input shaft of the transmission. Oil from the shaftcools and lubricates the clutch assembly and input shaft bearings. Theoutput shaft, countershaft and reverse idler shaft are splash lubricated.The oil then returns to the sump.
Orifices in the solenoid valves provide for some clutch modulation whena speed and direction are selected.
The Autoshift ECM contains the software to control the shifting of thetransmission. The software compares the input information to the theinformation stored in the Autoshift ECM to determine the appropriategear for the machine.
The Autoshift ECM then sends output signal to energize solenoids for theappropriate clutch. Through ET, FIRST gear can be ENABLED orDISABLED.
FIRST gear is a relatively low (slow) gear ratio, and using it may not benecessary for normal loader work or for roading. If using AUTOSHIFTfor either loading or roading, disabling FIRST gear eliminates a extra gearshift. In extreme hard digging conditions, the neutralizer button can beused to downshift to FIRST, and then AUTOSHIFT will upshift thetransmission as the machine speed increases.
In summary, disabling FIRST makes the tractor more responsive,smoother, and efficient (more productive). Use FIRST gear only whenrequired.
NOTE: The lines and fittings from the torque converter and the oilcooler are sized to provide sufficient restriction to the oil in the torqueconverter. A torque converter outlet relief valve is not required.
The cold start relief valve between the pump and filter on the "C"Series has been removed on the "D" Series.
• Autoshift ECM
STMG 746 - 47 -10/02
30
• Autoshifttransmission - AWD
• SECOND SPEEDFORWARD:
- No. 1 and 4solenoids energized
3
2
REGULATEDPRESSURE
1
LUBETORQUE
CONVERTEROUTLET
TRANSMISSIONLUBE
SUCTIONSCREEN
LO
HIR
FORWARD
AUTOSHIFT POWER TRAINHYDRAULIC SYSTEM
ALL WHEEL DRIVE / SECOND FORWARD
6
ORIFICE
SOLENOIDVALVE
5 1 3 4
AUTO/MANUAL SWITCH
NEUTRAL LOCK SWITCH
RIDE CONTROL SWITCH
PARKING BRAKE SWITCH
DOWNSHIFT/NEUTRALIZER SWITCH
RIDE CONTROL DISABLE
2
DATA LINKSERVICE PORT
SHIFT LEVER
TRANSMISSION OUTPUT SPEED SENSOR
FILTER
PUMP TORQUECONVERTER
TORQUECONVERTER
INLETRELIEF VALVE
RELIEFVALVE
AWD
TORQUECONVERTER INLET
PUMPSUPPLY
AUTOSHIFTECM
OIL COOLER
Here is the power train hydraulic schematic for the autoshift transmissionequipped with All Wheel Drive (AWD).
The power train hydraulic system for AWD machines is the same as thetwo wheel drive machines except for the AWD solenoid and clutch.When the AWD solenoid is energized, oil engages the AWD clutch.
This schematic shows the No. 1 and No. 4 solenoids have been energizedto engage the forward high directional clutch and the No. 1 speed clutchto obtain SECOND SPEED FORWARD. The relief valve limits themaximum clutch pressure.
STMG 746 - 48 -10/02
31
• Autoshifttransmission logicchart
CLUTCH ENGAGEMENT
REVERSE
FORWARDHIGH
FORWARDLOW
CLUTCH 1
CLUTCH 3
CLUTCH 2
AWDCLUTCH
INPUTSHAFT
OUTPUTSHAFT
AWDSHAFT
COUNTERSHAFT
AUTOSHIFT TRANSMISSION
FWD FWDGEAR LOW HIGH REV 1 2 3
5F X X 1 AND 6
4F X X 1 AND 5
3F X X 3 AND 5
2F X X 1 AND 4
1F X X 3 AND 4
N – –
1R X X 2 AND 4
2R X X 2 AND 5
3R X X 2 AND 6
SOLENOID
The five-speeds forward, three-speeds reverse transmission is equippedwith six clutch packs. The autoshift transmission uses six solenoids tocontrol the engagement of the clutch packs. Two clutch packs must besimultaneously engaged for the transmission to drive the machine. Theabove chart shows the energized solenoids and the engaged clutch packsfor each gear. The solenoids are controlled by the Autoshift ECM.
In NEUTRAL, none of the solenoids are energized.
The chart can be used to identify which solenoids are energized to engagethe speed and direction clutches to obtain the desired speed range.
NOTE: The Autoshift ECM does not provide shift protection on the"D" Series. Some shift protection is provided for the 446B backhoeloader. Shift protection prevents the operator from changingdirections at high speeds.
STMG 746 - 49 -10/02
32
• Autoshift ECMoperation
AUTO/MANUALSWITCH
PARKING BRAKESWITCH
RIDE CONTROLSWITCH
NEUTRAL LOCKSWITCH
TRANSMISSION OUTPUTSPEED SENSOR
RIDE CONTROLDISABLE SWITCH
SHIFT
LEVER
CONTROL
LOADER LOCKRELAY
BACKUPALARM
STARTRELAY
KEY STARTSWITCH
SPEED CLUTCH 2No. 5 SOLENOID
FORWARD LOWNo. 3 SOLENOID
PARK BRAKEALARM RELAY
FORWARD HIGHNo. 1 SOLENOID
REVERSENo. 2 SOLENOID
SPEED CLUTCH 1No. 4 SOLENOID
SPEED CLUTCH 3No. 6 SOLENOID
DIAGNOSTICINDICATOR and
DATA LINKSERVICE PORT
AUTOSHIFT
ELECTRONIC
CONTROL
MODULE
CAT DATA LINK
RIDE CONTROLRELAY
DOWNSHIFT/NEUTRALIZER SWITCH
AUTOSHIFT ELECTRONIC TRANSMISSION CONTROL SYSTEM
The Autoshift ECM has two modes of operation: Automatic and Manual.
In the Automatic Mode of operation, the operator controls the highestdesired gear and the transmission control automatically selects the propergear based on machine ground speed. The transmission determines theground speed through the transmission speed sensors and energized speedclutch.
In the Manual Mode, the transmission operates very similar to thestandard power shift transmission. In this presentation, the AutomaticMode will be discussed except where it is stated that the Manual Mode isbeing discussed.
➥
STMG 746 - 50 -10/02
When the key start switch is ON, the transmission shift lever controlprovides input to the Autoshift ECM through the CAT Datalink. TheAutoshift ECM uses the input from the shift lever control to determine thegear range selected on the transmission shift lever control and the positionof the key start switch.
When the key start switch is moved into the START position, the key startswitch directs power to the shift lever control. The shift lever control,must be in NEUTRAL to signal the Autoshift ECM that the key startswitch is in the START position. The shift lever control completes thecircuit between the key start switch and the start relay. The start relay isenergized, allowing power to the starter to crank the engine.
If the shift lever control is not in NEUTRAL during starting, the AutoshiftECM will prevent the machine from starting.
The parking brake switch provides an input signal to the Autoshift ECM.The parking brake switch is closed when the parking brake is ENGAGEDand open when the parking brake is RELEASED.
If the shift lever control is in NEUTRAL with the parking brakeENGAGED and is then moved out of NEUTRAL, the Autoshift ECMprevents the transmission from shifting and energizes the parking brakerelay to sound the alarm.
The Autoshift ECM will allow the transmission to shift when the parkingbrake is ENGAGED if the shift lever control is cycled into and out of theNEUTRAL position twice within a span of three seconds. If the shiftlever control is shifted from NEUTRAL when the parking brake isENGAGED, the Autoshift ECM records a parking brake event.
When the parking brake is RELEASED and the shift lever control ismoved out of the NEUTRAL position, the Autoshift ECM directs outputsignals to the appropriate transmission control solenoids. The AutoshiftECM energizes one speed and one directional solenoid to engage clutchesin the transmission.
STMG 746 - 50 -10/02
• Parking brake switch:
- Signals AutoshiftECM
- Autoshift ECMpreventstransmission fromshifting if parkingbrake ENGAGED
• Shift lever control:
- Inputs in AutoshiftECM through CatDatalink
➥
STMG 746 - 51 -10/02
If the parking brake is ENGAGED while the transmission is in a gear, theECM shifts the transmission into NEUTRAL and energizes the parkingbrake relay. The transmission will remain in NEUTRAL until the shiftlever control is moved into the NEUTRAL position and the parking brakeis RELEASED. The shift lever control can then be used to select a gear.
The transmission neutral lock switch also provides an input signal to theAutoshift ECM. If the transmission neutral lock switch is moved to theLOCK position, the Autoshift ECM shifts the transmission intoNEUTRAL and prevents the transmission from shifting, regardless of theposition of the shift lever control. The Autoshift ECM will not shift thetransmission until after the shift lever control is moved into theNEUTRAL position and the transmission neutral lock switch is moved tothe UNLOCK position.
The transmission is neutralized as soon as the neutralizer/downshiftbutton is pressed. If the button is released within one second, thetransmission is downshifted one gear by moving from the neutralizedstate to the downshifted state. If the button is held for more than onesecond, the transmission will remain neutralized until the button isreleased.
When the transmission is downshifted with the downshift function, thetransmission control will hold the machine in the downshifted gear forfive seconds before the machine returns to the Automatic Mode. Thedownshift function is implemented by the Neutralizer/Downshift input,which is a dual function input.
When downshifted, with the shifter in the third or fourth position, theAutoshift ECM downshifts the transmission one gear per actuation of thebutton.
If the operator gives multiple downshift commands, within five seconds,the transmission will be downshifted once in response to the firstcommand. The machine will downshift again if transmission outputspeed is below runout speed for the next lower gear.
If the machine is above the runout speed for the next lower gear, thetransmission control will not downshift until the machine is below therunout speed. If the transmission is in FIRST gear when a downshiftcommand is issued, the command will be ignored.
STMG 746 - 51 -10/02
• Transmissiondownshift/neutralizerswitch
• Transmission neutrallock switch
- Neutralizestransmission inLOCK position
- Downshift function
➥
STMG 746 - 52 -10/02
- Neutralizer function
If the shift lever is in SECOND, the downshift button will force themachine to be downshifted at once and held in FIRST until a speed ordirection change or the five second delay is over.
When a neutralizer request is initiated by the operator, the transmissionwill momentarily neutralize by de-energizing the direction clutch. Onlythe directional clutch is de-energized. This will improve shift speed whenthe button is released and the machine is placed back into gear.
In the Manual Mode, the Downshift/Neutralizer Switch will not permit thetransmission to be downshifted.
The transmission speed sensor provides output speed information to theAutoshift ECM. In the Automatic Mode of operation, the operatorcontrols the highest desired gear and the transmission controlautomatically selects the proper gear based on machine ground speed.The Autoshift ECM determines the ground speed through the transmissionspeed sensors and energized speed clutch.
If the machine is in FOURTH, as the ground speed increases, third gearmay be skipped as the machine upshifts. This is done through thesoftware to improve shift performance. This feature is called Skip-ShiftLogic. In Auto Mode, 3rd gear can be skipped on up-shifts only, allowingthe transmission to shift from 2nd to 4th. If the 2nd to 4th shift point isnot reached in a specific amount of time (0-1sec) the transmission willshift to 3rd gear. The default mode for the skip-shift is to have the timervalue set to zero (disabled). There is a configuration option through ET toallow for enabling of Skip-Shift.
If desired, fifth gear may be enabled or disabled through ET in order tocomply with regulations in certain countries.
The dead engine lower (loader lock) relay is part of the loader lock valveattachment to control the loader hydraulic lock valves. The input from theloader lock relay is used by the Autoshift ECM to determine if the startrelay should be energized. If the loader control lever is in the "FLOAT"position the Autoshift ECM will not allow the machine to start. Thisaction prevents the loader arms from unexpectedly lowering duringmachine start-up when the machine is equipped with hydraulic lockvalves.
NOTE: Fourth gear may also be enabled or disabled through ET.
STMG 746 - 52 -10/02
• Transmission speedsensor:
- Provides input toAutoshift ECM
- Autoshift ECM usesinput to determinedownshifts
• Dead engine lowerrelay
With FIRST gear enabled, the following gears are available in the givenconditions.
Shift lever in FIRST: The transmission will be held in FIRST gear.
Shift lever in SECOND: The transmission will automatically shiftbetween FIRST and SECOND in response to machine speed.
Shift lever in THIRD: The transmission will automatically shiftbetween FIRST, SECOND and THIRD in response to machine speed.The downshift switch can be used to force the transmission into FIRST orSECOND gear.
Shift lever in FOURTH: The transmission will automatically shiftbetween FIRST through FIFTH in response to machine speed. THIRDgear may be skipped by the software. The downshift switch can be usedto force the transmission into FIRST, SECOND, THIRD or FOURTHgear.
Whenever a machine is downshifted into a lower gear, the machinemaximum gear will be limited to the lower gear for five seconds, thenreturn to normal Automatic Mode.
STMG 746 - 53 -10/02
1ST GEAR ENABLEDAUTOSHIFT TRANSMISSION
SHIFT LEVERPOSITION
GEARSAVAILABLE
4F
3F
2F
1F
N1R
2R
3R
1, 2, 3, 4, 5
1, 2, 3
1, 2
1
1
1, 2
1, 2, 3
33
• Gear selection inAutoshift (FIRST gearis enabled)
STMG 746 - 54 -10/02
34
With FIRST gear disabled, the following gears are available in the givenconditions.
Shift lever in FIRST: The transmission will be held in FIRST.
Shift lever in SECOND: The transmission will be held in SECONDunless the operator forces the transmission into FIRST through thedownshift switch.
Shift lever in THIRD: The transmission will automatically shiftbetween SECOND and THIRD in response to machine speed. Thedownshift switch can be used to force the transmission into FIRST orSECOND gear.
Shift lever in FOURTH: The transmission will automatically shiftbetween SECOND through FIFTH in response to machine speed. THIRDgear may be skipped by the software. The downshift switch can be usedto force the transmission into FIRST, SECOND, THIRD or FOURTHgear.
If the machine is downshifted into a lower gear, upshifts will be disabledfor five seconds, then return to normal Automatic Mode.
STMG 746 - 54 -10/02
1ST GEAR DISABLEDAUTOSHIFT TRANSMISSION
SHIFT LEVERPOSITION
GEARSAVAILABLE
4F
3F
2F
1F
N1R
2R
3R
2, 3, 4, 5
2, 3
2
1
1
2
2, 3
• Gear selection inAutoshift (FIRST gearis disabled)
STMG 746 - 55 -10/02
• Features:
- Hydraulicallyengaged brakessame as "B" and "C"Series
- Differential locksame as "B" and "C"Series
35
Axles and Brakes
The standard rear axle is similar to the "B" and "C" Series.
Differential lock operation and power flow through the rear axle are thesame as with the "B" and "C" Series.
The hydraulically engaged brakes are the same as "B" and "C" Series.
If the machine is equipped with All Wheel Steer, an axle with a limitedslip differential is used instead of differential lock.
BEVEL GEARDIFFERENTIAL
ASSEMBLY
FIXED RINGGEAR
PINION GEARAND SHAFT
DIFFERENTIAL LOCKACTUATOR
DIFFERENTIAL LOCKASSEMBLY
MULTI-DISCBRAKE ASSEMBLY
PLANETGEAR
FROMMASTER
CYLINDER
REAR AXLE
STMG 746 - 56 -10/02
• Brake mastercylinders:
- Left and right mastercylinders the same
- Reservoir suppliesmaster cylinder
• ENGAGED
36
This illustration shows the master cylinders. Both the right and leftmaster cylinders are the same. Fluid from the brake fluid reservoir enterseach master cylinder through the supply port. Fluid from the reservoirfills the spring chamber and the supply line to the brake piston. Thespring and plunger prevent the valve stem from closing the supply port.
When the operator depresses one of the brake pedals, the push rod movesagainst the plunger. As the plunger moves to the up, trapped oil inside theplunger moves the valve stem up to block the supply port. Fluid pressurein the spring chamber increases. As fluid pressure in the spring chamberincreases, the pressure unseats the compensation valve on the leftallowing oil to flow to the other master cylinder through the bridge pipe.
FROMRESERVOIR
SUPPLY PORT
TO BRAKEPISTON
PLUNGER
PUSH ROD
VALVE STEM
TO BRAKEPISTON
PLUNGER
BRIDGE PIPE
COMPENSATIONVALVE
RIGHT BRAKERELEASED
LEFT BRAKEENGAGED
BRAKE MASTER CYLINDERS
➥
STMG 746 - 57 -10/02
The compensation valve in the right master cylinder blocks the oil in thebridge pipe from entering the right master cylinder. As the plungercontinues to move up, it will eventually block the inlet to thecompensation valve.
At the same time that oil enters the compensation valve, oil enters theoutlet pipe to the brake piston.
As pressure increases behind the brake piston, the piston pushes the discsand plates together against the brake housing to ENGAGE the brake.
If the operator engages both brakes simultaneously, both compensationvalves open allowing the pressure in the spring chamber of both mastercylinders to equalize.
The distance the operator depresses the brake pedal determines thepressure that the piston exerts on the plates and discs. The farther theoperator pushes the brake pedal, the more pressure the piston applies tothe plates and discs and, therefore, the greater the braking force.
When the operator releases the brake pedal, the spring in the mastercylinder moves the valve stem away from the inlet port reducing thepressure behind the brake piston. A seal around the piston moves thepiston away from the discs and plates to RELEASE the brakes.
The same brake valve is used on machines equipped with All Wheel Steer(AWS).
• RELEASED
• AWS
STMG 746 - 58 -10/02
37
• Rear axlecomponents:
1. Hose from mastercylinder
2. Differential locklinkage
3. Parking brake disc
4. Parking brake padassembly
On the rear axle, the hose (1) is connected to the the master cylinderoutlet pipes and directs oil to the brake actuator pistons. A bleed screw(not shown) next to the hose allows bleeding of the brake lines.
Mechanical linkage from the parking brake lever engages the caliper anddisc-type parking brake (3 and 4). The parking brake is on the drive shaftbetween the transmission and the rear axle. The parking brake needs tobe checked and possibly adjusted at regular intervals.
1
2
3
4
STMG 746 - 59 -10/02
38
• Power traincomponents:
1. Brake mastercylinders
2. Brake pedals
3. Differential lockpedal
The machine contains two master cylinders (1), one for each brake pedal(2).
The master cylinders can be removed from the machine from inside theoperator's compartment. Due to a design change, the brake cylinders nolonger have to be removed before removing the cab as required on the"C" Series.
1
23
STMG 746 - 60 -10/02
• AWD axlecomponents
39
The AWD axle is equipped with a conventional bevel and pinion geardifferential. The final drive consists of an outboard planetary geararrangement in each wheel hub.
PINION GEARAND SHAFT
BEVELGEAR
DIFFERENTIAL
LEFT DRIVEAXLE
PLANETGEAR
SUN GEARAND SHAFT
RING GEAR
LEFT DRIVEJOINT
LEFT STEERKNUCKLE HOUSING KING
PINS
AWD FRONT AXLE
STMG 746 - 61 -10/02
40
• AWD front axle:
1. Sealed andlubricated pin
2. Steering cylinder
3. Drain plug
AWD axle is available as an option to replace the standard axle.
The axle is pendulum mounted. The pin (1) is permanently sealed andlubricated. The steering cylinder (2) is mounted to the front of the axle.
The standard axle is also permanently sealed and lubricated. The steeringcylinder is mounted to the rear of the axle.
1
23
STMG 746 - 62 -10/02
• 416D hydraulicsystem:
- Center pivot
- Mechanical controls
41
STEERING AND IMPLEMENT HYDRAULIC SYSTEMS
The "D" Series backhoe hydraulic systems incorporate many of theimprovements made to late production "C" Series.
The illustration represents the 416D steering and implement hydraulicsystem.
The steering and implement pump, the pump control and most of theimplement control valves function essentially the same. The biggestdifference to the implement valves is that on some models they are pilotoperated. Also, on some models the operating pressures have also beenincreased.
On the "D" Series, the stabilizer valves are pilot controlled and are of adifferent design from previous backhoe loader stabilizer valves.
SMU
LIFT
TILT
AUX
STEER
STICK
ENDCOVER
SWING
E-STICK
PUMP
TANK
BOOM
BUCKET
INLETMANIFOLD
AUX
LEVERLEFT
STABILIZER
RIGHTSTABILIZER
MANIFOLD LEVER
BACK FLOWCHECKVALVE
COOLER
416D CENTER PIVOT BACKHOE LOADERHYDRAULIC SYSTEM
➥
STMG 746 - 63 -10/02
The steering system features dynamic signal bleed as did the lateproduction "C" Series. With the dynamic bleed and the steering inHOLD, the steering priority spool bleeds oil through the steering meteringunit (SMU) signal line and SMU back to the tank. When the steeringwheel is turned, this signal bleed oil shifts the priority spool to directpump supply oil to the SMU resulting in faster steering response thansystems without dynamic bleed.
The hydraulic tank has also been redesigned. An expansion tank is nolonger required.
The backflow check valve has been relocated. The valve now restrictsreturn flow from all implement valve groups. On previous backhoes, thevalve only worked with the backhoe valve group. The valve assists inpreventing cylinder voiding. The check valve does not affect return oilfrom the SMU.
The other major difference in the hydraulic system is the signal networkrouting, which is referred to as "reverse signal path." The signal networkwill be described later in this presentation.
NOTE: The colors on the hydraulic schematics and cross-sectionalviews shown throughout this presentation denote various pressureswithin the system. The legend of color codes is as follows:
Red - pump supply pressure
Red and white stripes - reduced pump supply pressure, circuitpressure or load sensing pressure
Red hatch - further reduced pump supply pressure,circuit pressure or load sensing pressure
Pink - lowest pump supply pressure, circuitpressure or load sensing pressure
Orange - signal or pilot pressure
Orange and white stripes - a lower signal or pilot pressure
Orange hatch - further reduced signal pressure
Green - line open to the tank
Blue - blocked oil
Yellow - moving part or active valve envelope.
For metering situations more than one envelope may be highlightedin yellow.
STMG 746 - 64 -10/02
• 424D, 428D and 438Dhydraulic system:
- Sideshift machines
- Mechanical controls
42
The 424D, 428D and 438D sideshift machines have similar componentsas the center pivot machines. The sideshift machines are equipped withsideshift lock pistons.
The 424D is not available with two loader bucket tilt cylinders as shownhere.
Some countries require a shutoff valve to block the flow of oil to thebackhoe valve group when the machine is roaded to prevent unintentionalimplement movement. Center pivot machines may also be equipped withthis feature.
The shutoff valve is an option on those machines with mechanicalimplement controls only.
SHUTOFF
SMU
LIFT
TILT
AUX
STEER
STICK
ENDCOVER
SWING
E-STICK
PUMP
TANK
BOOM
BUCKET
INLETMANIFOLD
AUX
LEVERLEFT
STABILIZER
RIGHTSTABILIZER
MANIFOLD LEVER
BACK FLOWCHECKVALVE
COOLER
SIDESHIFTLOCK PISTONS
424D / 428D / 438D SIDE SHIFT BACKHOE LOADERSHYDRAULIC SYSTEM
RIDECONTROL
JOYSTICK
LEVER
JOY
ST
ICK
SMU
LIFT
TILT
AUX
STEER
STICK
ENDCOVER
SWING
E-STICK
PUMP
TANK
BOOM
BUCKET
INLETMANIFOLD
AUX
LEFTSTABILIZER
RIGHTSTABILIZER
MANIFOLD
JOY
ST
ICK
LEVER
PILOTSHUTOFF
BACK FLOWCHECKVALVE
COOLER
PA
TT
ER
N C
HA
NG
ER
420D / 430D CENTER PIVOT BACKHOE LOADERS HYDRAULIC SYSTEMPARALLEL LIFT
STMG 746 - 65 -10/02
43
• 420D and 430Dhydraulic system:
- Center pivotmachines
- Pilot controls
The backhoe valves on the 420D and 430D are pilot operated. If themachine is equipped with IT linkage, as shown, then the loader valves arealso pilot operated. With pilot operated machines a pilot accumulator isused to provide dead engine lowering capability for a limited time afterengine shutdown.
These machines ship with the excavator control pattern. Machines can beordered with the standard backhoe control pattern or ordered with anoptional pattern changer valve.
If the machine is equipped with the single tilt cylinder bucket, the loadervalves are operated through mechanical linkage instead of a pilot joystick.
The pilot shutoff valve blocks the oil from the joysticks to preventmovement of an implement. The shutoff valve eliminates the need of theoptional hydraulic shutoff valve available on machines with mechanicalcontrols only.
STMG 746 - 66 -10/02
• 432D and 442Dhydraulic system:
- Sideshift machines
- Pilot controls
44
The backhoe valves on the 432D and 442D are pilot operated. The loadervalves are also pilot operated since the standard version of these modelsfeature the IT linkage.
The single tilt cylinder bucket is optional. With this option the loadervalves are operated through mechanical linkage.
Ride control is an option that is available for all "D" Series backhoes.Hose routing and the system design has changed from the "C" Series.
JOYSTICK
LEVER
JOY
ST
ICK
SMU
LIFT
TILT
AUX
STEER
STICK
ENDCOVER
SWING
E-STICK
PUMP
TANK
BOOM
BUCKET
INLETMANIFOLD
AUX
LEFTSTABILIZER
RIGHTSTABILIZER
MANIFOLD
JOY
ST
ICK
LEVER
PILOTSHUTOFF RIDE
CONTROL
BACK FLOWCHECKVALVE
COOLER
SIDESHIFTLOCK CYLINDERS
PA
TT
ER
N C
HA
NG
ER
432D / 442D SIDESHIFT BACKHOE LOADERS HYDRAULIC SYSTEMPARALLEL LIFT
STMG 746 - 67 -10/02
• Signal network:
- Reverse signal path
- Affects resolvertroubleshooting
- Orificed steeringresolver
- Orifices in loaderprimary resolvers
45
On most generations of backhoes, the signal line was routed from thebackhoe section, to the loader section and then to the pump. Lateproduction "C" Series had a variation from this with a signal line from thebackhoe section and a signal line from the loader section being connectedto a tee which was equipped with a resolver. The highest resolved signalbetween the two valve sections then flows to the pump.
With the "D" Series, the last resolver in the network is in the loaderauxiliary circuit. The signal flows from the loader section, to thestabilizer section, to the backhoe section, before going to the pump controlvalve. This routing is reverse of previous backhoe signal networks.
Resolver troubleshooting procedures are affected by this change. Asecondary resolver problem in the loader section will no longer have anaffect on the backhoe section.
RIGHTSTABILIZER
LEFTSTABILIZER
"D" SERIES BACKHOE LOADER SIGNAL NETWORKMECHANICAL CONTROLLED LOADER VALVES
TORQUELIMITER
PUMPCONTROL
VALVE
CONNECTED TOSWASHPLATE
LOADERAUX.
LOADERTILT
SMULOADERLIFT
LOADER SECTION
BOOM
PRIMARYRESOLVER
SECONDARYRESOLVER
SWING BUCKET STICK
ORIFICE
BACKHOE SECTION
E-STICKAUX
➥
STMG 746 - 68 -10/02
The orifice in the steering resolver in the loader section results in a largerpressure differential across each loader resolver orifice when a loaderimplement is activated and the torque limiter opens, as compared to abackhoe implement. This difference in pressure results in a reducedsignal to the torque limiter and pump compensator.
This action provides for lower pump flow to the loader section for a givencircuit pressure when the torque limiter opens, which results in a loweravailable torque for the loader section than what is available for thebackhoe section. This change was done to further improve loader andbackhoe performance.
Backhoe implements (except for the auxiliary circuits) do not haveorifices in their primary resolvers and are not affected by the orifice in thesteering resolver.
An additional orifice was added between the backhoe valve section andthe orifice in the torque limiter for the "D" Series backhoe to furtherimprove machine performance.
STMG 746 - 69 -10/02
• Signal network:
- Pilot operated loadervalves
46
On machines with pilot operated loader valves, the pilot valve for theloader lift circuit is also part of the signal network.
The lift pilot valve directs some pilot oil through the resolver network toupstroke the pump when the loader is in FLOAT.
This pilot signal through the signal network causes the pump to increasepump standby pressure to make sure that pilot system pressure remainshigh enough to hold the lift spool in the FLOAT position.
NOTE: Since the maximum pilot pressure is limited, the pumpreceives a virtually fixed signal from the pilot system when the liftspool is shifted to FLOAT. This increase in pump supply and signalpressure can be checked at the pump outlet test fitting and the signaltest fitting. There is no recommended specification or test for this.
TORQUELIMITER
PUMPCONTROL
VALVE
CONNECTED TOSWASHPLATE
LOADERAUX.
LOADERTILT
SMULOADERLIFT
LOADER SECTION
BOOMPRIMARYRESOLVER
SECONDARYRESOLVER
SWING BUCKET STICK
RIGHTSTABILIZER
LEFTSTABILIZER
ORIFICE
BACKHOE SECTION
E-STICKAUX
LIFT PILOTVALVE
PILOT OIL
"D" SERIES BACKHOE LOADER SIGNAL NETWORKPILOT CONTROLLED LOADER VALVES
STMG 746 - 70 -10/02
47
• Hydraulic systemcomponents:
1. Hydraulic tank
2. Sight gauge
3. Steering MeteringUnit (SMU)
4. Drain tube
The hydraulic tank (1) is located between the engine and the cab.
With the relocation of the brake master cylinders, the hydraulic tank wasredesigned for increased capacity. With the increase in capacity theoverflow or expansion tank is no longer required.
1
2
34
STMG 746 - 71 -10/02
48
• Hydraulic systemcomponents:
1. Hydraulic filter
2. Steering andimplement pump
3. Pump control valve
4. Signal pressuretest fitting
5. Loader valve group
6. Back flow checkvalve
In the pump control valve (3) are two spools. The flow compensator(margin spool) regulates output flow in response to the load signalreceived through the signal network. The flow supplied by the pump willbe the amount of flow required to keep supply pressure at a fixed valueabove the signal pressure. The difference between supply pressure andthe signal pressure is called "margin pressure." The flow compensatoralso controls low pressure standby pressure.
The pressure cutoff spool in the pump control valve limits maximumsystem pressure and serves as the relief valve for the system.
The back flow check valve (6) is part of the fitting just before thehydraulic filter (1). The check valve helps reduce cylinder cavitation.
Before performing any pump tests or making adjustments to the pumpcontrol valve, measure and record the machine cycle times. If the cycletimes are within specification, checking low pressure standby or marginpressure may not be required unless the system is overheating. Cycletime checks will also indicate if all or some of the implements in thesystem are operating within specification.
➥
• Pump and systemtests
1
2
3
4
5
6
STMG 746 - 72 -10/02
This information can be helpful in determining if the pump or theimplement is at fault. If all cycle times are too slow, margin pressure andlow pressure standby may be set too low. If the machine is tooresponsive, the margin pressure and low pressure standby may be set toohigh.
The pump supply pressure test fitting (not shown) can be used to checkmaximum system pressure or low pressure standby. The fitting can beaccessed from below the operator's compartment.
Use the signal pressure test fitting (4) to check the signal pressure or themaximum steering pressure. Signal pressure is compared to pump supplypressure to determine the margin pressure.
All return oil from the implements and steering flows back to the filterthrough the backflow check valve. Due to the dynamic bleed steering,low pressure standby is over 700 kPa (100 psi) higher than on most "C"Series backhoes.
NOTE: Due to the signal pressure limiter, the steering circuit iscommonly used to check margin pressure because the steering circuitpressure is below maximum system pressure.
Engineering is recommending a slightly different procedure forchecking margin pressure on "D" machines. The latestrecommendation is to lock the boom and move the boom lever aboutone third travel in the DOWN position.
If Standby Pressure is adjusted to about 3100 kPa (450 psi) or slightlyhigher, the need to adjust a check margin pressure may not benecessary.
Also, on the "D" Series, engineering is suggesting that circuit andsystem stall pressures be checked at the signal pressure test fitting.By doing this the confusion related to checking circuits with lowerpressure settings than the pressure cutoff on the pump may beeliminated. For circuits with higher line relief settings than thepressure cutoff, the pressures read at either test port should be thesame.
STMG 746 - 73 -10/02
49
• Hydraulic systemcomponents:
- Torque limiter(arrow)
A torque limiter (arrow) is used to control the pump. The torque limiterwill reduce maximum pump flow available as pressures increase toprevent engine stall.
The torque limiter provides improved hydraulic system performance withless engine horsepower. The torque limiter is adjustable. Before makingadjustment to the torque limiter, make sure low idle is set correctly.
NOTE: A quick check to make sure the torque limiter is operatingcorrectly on single tilt cylinder machines, is to operate the machine atlow idle. With the machine at normal operating temperatures, applythe service brakes and select SECOND FORWARD. Turn on airconditioner (if equipped) and accessories. Raise and rack back thebucket. If the engine stalls, the torque limiter may need to beadjusted.
For dual tilt cylinder machines, follow the same steps, except stall thebucket in the dump position, instead of racking back.
For more precise adjustment of the torque limiter follow theprocedures in the service manual. A torque converter stall testshould also be done before adjusting the torque limiter. The enginemay not be performing correctly.
STMG 746 - 74 -10/02
50
• LOW PRESSURESTANDBY:
- With dynamic signalbleed
TORQUELIMITER
BLEEDSIGNAL
FLOWCOMPENSATOR
PRESSURECUTOFF
PUMPOUTPUT
STEERING AND IMPLEMENT PUMPLOW PRESSURE STANDBY / DYNAMIC SIGNAL BLEED
Steering and Implement Pump Operation
With all implements in HOLD, the steering priority valve bleeds somesupply oil through a dynamic bleed orifice back to the tank through theSMU. This oil flow creates a low pressure signal which is sensed at thepump compensator.
The LOW PRESSURE STANDBY reading will be higher on "D" Series machines equipped with a dynamic signal bleed steeringsystem than on previous backhoes without this feature.
The spring setting of the torque limiter changes with the angle of theswashplate. As shown here, at minimum angle, the setting is atmaximum. As the swashplate angle is increased, the spring setting isreduced.
STMG 746 - 75 -10/02
• CONSTANT FLOW:
- Signal pressure plusspring equalssystem pressure
- Swashplate atconstant angle
51
The pump will UPSTROKE or DESTROKE to match changes in flowrequirements.
When pump flow matches system needs the pump supply pressure equalsthe sum of the load pressure plus the margin spring pressure. The marginspool is in a metering position and the system is stabilized.
CONSTANT FLOW is maintained until there is a change in system flowrequirements.
The difference between the signal pressure and the pump supply pressureis the value of the margin spring.
STEERING AND IMPLEMENT PUMPCONSTANT FLOW
FLOWCOMPENSATOR PRESSURE
CUTOFF
SIGNAL
PUMPOUTPUT
STMG 746 - 76 -10/02
• Pressure/Flow (P-Q)Curve:
- Sweeping curveshows torque limitercontrol
52
This illustration shows a Pressure/Flow (P-Q) Curve Chart for the steeringand implement pump. The purpose of the chart is to show how the torquelimiter affects the maximum flow rate for the loader and backhoe sectionswhen the torque limiter opens.
The sweeping curves show where the torque limiter has control over thepump flow. The torque limiter destrokes the pump as the system pressureincreases. The rate of destroke closely follows the torque curve of theengine.
While on the torque curve, if the system pressure decreases, the torquelimiter control will UPSTROKE the pump.
The flow compensator spool regulates pump flow when system pressureand flow requirements are below the curves. This is the area shown inyellow.
FLOW (Q)
PRESSURE (P)
BACKHOE
LOADER
TORQUE LIMITER CONTROL
FLOW COMPENSATOR CONTROL
➥
STMG 746 - 77 -10/02
NOTE: When the updated "C" Series was introduced, the torquelimiter was being promoted as having "dual settings." This was notthe case. The torque limiter has one physical setting. Due to theorifices as discussed earlier, the torque limiter responds as if it hadtwo different settings.
STMG 746 - 78 -10/02
53
• Torque limiter OPEN:
- Pressure settingvaries withswashplate angle
- Pressure dropacross orifice
- Reduction in signalpressure to flowcompensator
- Pump destrokes
- Input torque ismaintained
STEERING AND IMPLEMENT PUMPTORQUE LIMITER OPEN
FLOWCOMPENSATOR
PRESSURECUTOFF
PUMPOUTPUT
TORQUELIMITER
SIGNAL
The torque limiter monitors the pump swashplate angle and the pumpsignal pressure. The pressure setting of the torque limiter varies with theswashplate angle: the greater the swashplate angle, the lower the pressuresetting.
For example, if the pump is at full stroke, the torque limiter will begin todestroke the pump when system pressure increases above 15180 kPa(2200 psi). As system pressure continues to increase, the pump flow isfurther reduced. The allowable pump displacement is inverselyproportional to the pump discharge pressure: the higher the pressure, theless pump flow available.
When the torque limiter setting is reached, the torque limiter opens,directing some of the signal oil to the tank. A pressure drop occurs acrossthe orifice, resulting in a slight loss of the actual signal pressure. Theflow compensator spool will move up, allowing supply oil to the largeactuator piston. The pump will then destroke.
STMG 746 - 79 -10/02
54
• Torque limiter OPEN:
- Stays open whenhydraulic demand ator above torquecurve
- Two different torquecurves
STEERING AND IMPLEMENT PUMPTORQUE LIMITER CLOSED
FLOWCOMPENSATOR
PRESSURECUTOFF
PUMPOUTPUT
TORQUELIMITER
SIGNAL
The torque limiter remains open and works with the flow compensator foras long as the conditions for the hydraulic demand are "at" or "above" thetorque curve. If the load conditions are demanding a certain pressure, theoperator is requesting a certain flow by positioning the valve stem andthese conditions are "at" or "above" the torque curve, the torque limiter isopen.
In summary, full pump supply pressure is always available. However,flow is regulated to maintain a maximum input torque from the engine.
Due to the additional orifices in the loader resolvers, the torque limiter ineffect has two different torque curves: one for the loader and one for thebackhoe.
When the hydraulic demand falls below the conditions stated above, thetorque limiter closes and the flow compensator then has control over thepump swashplate to regulate pump flow to meet the required systempressure and flow demands.
• Torque limiterCLOSED:
- Flow compensatorcontrols swashplate
• Loader valve groupcomponents:
1. Inlet manifold andsteering priorityvalve
2. Loader lift controlvalve
3. Tilt control valve
4. Auxiliary valve
Loader Valve Groups and Steering System
The loader section consists of an inlet manifold (1) with a steering priorityvalve, a loader lift control valve (2), a tilt control valve (3) and an optionalauxiliary valve (4).
The implement valves shown are pilot operated.
STMG 746 - 80 -10/02
55
1
2
34
STMG 746 - 81 -10/02
56
• Steering priority valveoperation:
- With dynamic signalbleed orifice
- Flow to implements
STEERING PRIORITY VALVEDYNAMIC SIGNAL BLEED
FROMPUMP
TO SMU
DYNAMICBLEED ORIFICE
TOSMU
TO PUMP
TO LOADERVALVES
FLOW TO IMPLEMENTS
TOTANK
FROMPUMP
TO LOADERVALVES
SIGNALPRESSURE
LIMITER
TOTANK
DYNAMICBLEED
ORIFICE
TOSMU
TO PUMP
FROMPREVIOUS
VALVE
PRIORITYSPOOL
SPRING
RESOLVER
TO SMU
FROMPREVIOUS
VALVE
FLOW TO SMU
The loader inlet manifold and steering priority valve are shown in twodifferent conditions. One condition shows flow to the implements and theother shows flow to the SMU.
Before the engine is started, the spring holds the priority spool to the left.When the engine is started, the flow from the pump is directed to thepriority valve. With the spool to the left, the pump supply oil is directedto the SMU. As the SMU passage fills, oil also enters the axial-drilledhole in the priority spool and flows to the left end of the spool.
As pressure builds on the left end, the spool starts to move to the right,against the force of the spring. The spool begins to restrict the oil flow tothe SMU supply passage as the spool continues to move to the right. Oilrestricted by the priority spool from entering the SMU supply passageflows to the loader implement valves.
➥
STMG 746 - 82 -10/02
- Dynamic bleedorifice
The priority spool never completely blocks the flow of oil to the SMUsupply passage. A small amount of oil is allowed to flow through thedynamic bleed orifice to the priority spool spring cavity where it becomessignal oil.
Signal oil flows from the spring cavity through the SMU signal line to theSMU, where the oil flows to the tank. This action causes the priorityspool to meter oil continuously to the SMU supply passage to maintain apredetermined pressure in the SMU supply passage. This pressureprovides instantaneous steering response when the steering is activated.The metering action also reduces spool travel when steering is required,which results in faster steering response.
With all implements in HOLD in this closed-center system, this signal oilis sensed at the pump control valve resulting in an increase in the LOWPRESSURE STANDBY setting.
If flow is not needed for steering and an implement valve in the loadersection is activated, the priority valve will direct most of the supply oil tothe loader implement circuits.
When the steering wheel is turned, more flow is needed at the SMU; thiscauses a momentary drop in pressure in the SMU supply passage.Pressure on the left side of the priority spool is also reduced.
The signal bleed pressure oil in the spring cavity and the priority springmove the spool to the left, blocking flow to the implements. As the pumpflow increases and supply oil enters the SMU passage, pressure increasesin the SMU passage and on the left end of the priority spool. As theforces on both ends of the spool equalize, the spool moves to a positionwhich enables it to maintain the flow requirements of the steering circuit.
As previously stated, the signal oil originates in the priority valve springcavity. From there, the signal goes to the resolver and to the SMU. Atthe SMU, the signal line is connected to the pressurized cylinder port (leftor right). From the resolver, the signal oil flows to the pump controlvalve. The pump then increases flow to meet the steering system flowrequirements.
Because the priority spool gives preference to the SMU supply circuit,flow may be blocked or metered to the loader implement valves.
- Oil flow to SMU
➥
STMG 746 - 83 -10/02
A signal pressure limiter valve limits the steering signal to protect thevarious steering components. When the signal pressure reaches apredetermined limit, the poppet in the signal pressure limiter moves to theright, opening a passage to the tank.
The spool moves back to the right and blocks flow from going to theSMU.
- Signal pressurelimiter valve
STMG 746 - 84 -10/02
57
• Steering circuit:
- Signal oil sent toSMU from priorityvalve
- Also enters signalnetwork
- SMU directs oil tosteering cylinder
STEERING CIRCUITTURN
STEERING METERINGUNIT
PUMPSUPPLY
FROMPREVIOUS
VALVE
TOLOADERVALVES
TO PUMPCOMPENSATOR
CHECKVALVE
MAKEUPVALVE
STEERING PRIORITY VALVE
This illustration shows the steering system during a TURN. Signal oil issent from the steering priority valve past the check valve to the SMUwhere the oil combines with the cylinder oil. The pressure in the SMUsignal line is limited to the steering cylinder port pressure. The signal oilalso enters the the signal network and flows to the pump control valve.The pump then increases flow to meet the steering system flowrequirements.
Oil from the pump flows past the steering priority valve to the SMU andto the double rod steering cylinder. When the machine makes a TURN,the SMU directs oil to the left side of the cylinder piston and opens theright side to the tank. A TURN in the other direction operates inversely.
The check valve in the pump supply line between the SMU and the loadervalve inlet manifold prevents steering "kickback" due to an external force.The makeup valve provides steering capability when the engine is notrunning by allowing oil to recirculate between the SMU and the steeringcylinder when the steering wheel is turned.
• Check valve prevents"kickback"
• Makeup valveprovides steeringcapability if the enginestops
STMG 746 - 85 -10/02
• Loader valveoperation:
- Mechanical controls
58
The following seven illustrations will cover the remaining valves in theloader valve group that are all mechanically operated.
All of the valves in the loader valve group are closed-center and pressurecompensated.
INSTRUCTOR NOTE: Components shown in yellow are shown onblock diagrams throughout this presentation. These diagrams are tobe used to introduce different sections of the hydraulic systemdiscussed in this presentation.
SMU
LIFT
TILT
AUX
STICK
ENDCOVER
SWING
E-STICK
PUMP
TANK
BOOM
BUCKET
INLETMANIFOLD
AUX
LEFTSTABILIZER
RIGHTSTABILIZER
MANIFOLD
BACKFLOWCHECKVALVE
COOLER
STEER
LEVER
LEVER
"D" SERIES MECHANICALLY CONTROLLED LOADER VALVES
STMG 746 - 86 -10/02
59
• Loader lift controlvalve in HOLD:
- Advance signalpassage for loaderRAISE
- Four position spool
- Mechanical balldetent for FLOAT
The loader lift control valve has a flow control spool and a makeup valveon the rod end work port. The main control spool also has an advancesignal passage to help raise the loader.
The loader lift control lever has four positions: RAISE, HOLD, LOWERand FLOAT.
INSTRUCTOR NOTE: For a detailed description of implementvalve operation used in the "D" Series, refer to STMG 630 "416B -438B Backhoe Loaders–Steering and Implement Hydraulic System"(Form SESV1630).
RODEND
HEADEND
FROMPREVIOUS
VALVE
TO STEERINGVALVE
PLUG
ADVANCESIGNAL
PASSAGE
BALLDETENT
LOADER LIFT CONTROL VALVEHOLD
FLOW CONTROLVALVE
FROMPUMP
STMG 746 - 87 -10/02
• 416D and 424D tiltcontrol valve in HOLD:
- Advance signalpassage for RACKBACK
- Three position spool
- Magnetic detent for"return to dig"feature
The 416D and 424D tilt control valve is used to control a single tiltcylinder.
The tilt control valve has a flow control spool and a pilot operated makeupand line relief valve for each work port. The main control spool has anadvance signal passage for the TILT BACK or RACK BACK function.The control spool has a magnetic detent (solenoid) that is part of the"return to dig" feature.
The loader tilt control lever has three positions: RACK BACK, HOLDand DUMP.
60
FROMPREVIOUS
VALVE
TO NEXTVALVE
ADVANCESIGNAL
PASSAGE
SOLENOIDDETENT
RODEND
HEADEND
FLOW CONTROLVALVE
LINE RELIEF ANDMAKEUP VALVE
FROMPUMP
416D AND 424D LOADER TILT CONTROL VALVEHOLD
STMG 746 - 88 -10/02
• 428D and 438D tiltvalve for parallel lift inHOLD:
- Four position spool
- Magnetic detent for"return to dig"feature
61
The 428D and 438D tilt control valve is used to control two tilt cylinders.
The loader parallel tilt control lever has four positions: RACK BACK,HOLD, DUMP and REGENERATIVE DUMP.
The valve has a magnetic detent for "return to dig."
FROMPREVIOUS
VALVE
TO LIFTVALVE
SOLENOIDDETENT
FLOW CONTROL VALVE
LINE RELIEF ANDMAKEUP VALVE
FROM PUMP
428D AND 438D LOADER TILT CONTROL VALVE FOR PARALLEL LIFTHOLD
HEADEND
RODEND
STMG 746 - 89 -10/02
• Parallel lift inREGENERATIVEDUMP
62
The force of gravity tends to cause implements to lower faster than thehydraulic pump and makeup valves can fill the cylinders. A"REGENERATIVE DUMP" position can reduce this tendency.
Due to the lands of the tilt valve, return oil from Port "B" cannot go to thetank. The return oil from the implement is directed through the bridgepassage to Port "A" when the control spool is shifted to theREGENERATIVE DUMP position. This position allows the bucket to bepowered down by pump flow. This action prevents cylinder cavitationand causes the bucket to dump faster.
NOTE: The line relief valve settings are set lower than maximumsystem pressure on machines equipped with parallel lift.
FROMPREVIOUS
VALVE
TO LIFTVALVE
SOLENOIDDETENT
FLOW CONTROLVALVE
LINE RELIEF ANDMAKEUP VALVE
FROM PUMP
HEADEND
RODEND
428D AND 438 LOADER TILT CONTROL VALVE FOR PARALLEL LIFTREGENERATIVE DUMP
STMG 746 - 90 -10/02
• 416D and 424D loaderauxiliary control valvein HOLD:
- Used for MP bucket
- Three position spool
The 416D and 424D loader auxiliary valve is typically used for the Multi-Purpose (MP) Bucket.
The loader auxiliary control valve has a flow control spool and a pilotoperated makeup and line relief valve for the rod end work port.
The loader tilt control lever has three positions: OPEN, HOLD andCLOSE.
63
FROM PUMP
TO NEXTVALVE
PORTA
PORTB
FLOW CONTROLVALVE
LINE RELIEF ANDMAKEUP VALVE
416D AND 424D AUXILIARY CONTROL VALVEHOLD
STMG 746 - 91 -10/02
• 428D and 438Dparallel lift loaderauxiliary control valvein HOLD:
- Three position spool
- Line relief andmakeup valve
- Solenoid detent
64
The 428D and 438D loader auxiliary control valve provides moreversatility than the 416D and 428D loader auxiliary control valve.
The loader auxiliary control valve has a flow control spool and a pilotoperated makeup and line relief valve for the rod end work port.
The auxiliary control lever has three positions.
A solenoid detent is also used for applications requiring continuous flow.
SOLENOIDDETENT
LINE RELIEF ANDMAKEUP VALVE
FLOWCONTROL
VALVE
CONTROLSPOOL
TO NEXTVALVE
PORTB
PORTA
FROMPUMP
RESOLVERS
428D AND 438D AUXILIARY CONTROL VALVE FOR PARALLEL LIFTHOLD
STMG 746 - 92 -10/02
65
• Single tilt cylinderloader:
1. Microswitch
2. Loader linkage arm
The loader linkage arm (2) has been redesigned for improved reliability.
The microswitch (1) rides along a cam machined into the bucket link.The switch works with a solenoid on the bucket control valve to providethe "return to dig" feature.
1
2
STMG 746 - 93 -10/02
66
LEVER
RIDECONTROL
JOYSTICK
LEVERJO
YS
TIC
K
SMU
LIFT
TILT
AUX
STEER
STICK
ENDCOVER
SWING
E-STICK
PUMP
TANK
BOOM
BUCKET
INLETMANIFOLD
AUX
LEFTSTABILIZER
RIGHTSTABILIZER
MANIFOLD
JOY
ST
ICK
LEVER
PILOTSHUTOFF
BACKFLOWCHECKVALVE
COOLER
PA
TT
ER
N C
HA
NG
ER
"D" SERIES PILOT CONTROLLED LOADER VALVES
• Loader valveoperation:
- Pilot controls
The following 14 illustrations will cover the valves in the loader valvegroup that are pilot operated along with their related components.
The internal components of the pilot controlled implement valve arebasically the same as the mechanically controlled implement control valveexcept for the difference in how the valves are controlled.
All of the valves are closed-center and pressure compensated.
STMG 746 - 94 -10/02
• Loader lift controlvalve in HOLD:
- Advance signalpassage for loaderRAISE
- Four position spool
67
The loader lift control valve has a flow control spool and a makeup valveon the rod end work port. The main control spool also has an advancesignal passage to help raise the loader.
The loader lift control lever has four positions: RAISE, HOLD, LOWERand FLOAT.
Pilot oil is directed to either end of the spool to shift the valve.
FLOW CONTROLVALVE
CONTROLSPOOL
TO NEXTVALVE
HEADEND
FROMPUMP
RESOLVERS RODEND
FROMPREVIOUS
VALVE
PILOTPASSAGE
ADVANCE SIGNALPASSAGE
LOADER LIFT CONTROL VALVEHOLD
STMG 746 - 95 -10/02
• Loader lift valve inFLOAT
68
For the FLOAT position, higher pilot pressure acting on the right end ofthe control spool moves the spool further to the left than for LOWER.
Both workports are open to the tank through passages in the valve.
A solenoid in the joystick maintains the spool in FLOAT position until theoperator shifts the spool to a different position.
FLOAT is used for "backdragging."
FLOW CONTROLVALVE
CONTROLSPOOL
TO NEXTVALVE
HEADEND
FROMPUMP
RESOLVERS RODEND
FROMPREVIOUS
VALVE
PILOTPASSAGE
ADVANCE SIGNALPASSAGE
LOADER LIFT CONTROL VALVEFLOAT
TANKPASSAGE
STMG 746 - 96 -10/02
• Tilt control valve inHOLD:
- Used with dual tiltcylinders
- Four position spool
69
This illustration shows the pilot operated tilt control valve used with thedual tilt cylinder configuration.
The tilt control valve has a flow control spool and a pilot operated makeupand line relief valve for each work port. The main control spool has anadvance signal passage for the TILT BACK or RACK BACK function.
The pilot joystick has a magnetic detent (solenoid) that is part of the"return to dig" feature.
The loader tilt control lever has four positions: RACK BACK, HOLD,DUMP and REGENERATIVE DUMP.
LINE RELIEF ANDMAKEUP VALVE
FLOW CONTROLVALVE
CONTROLSPOOL
FROMPREVIOUS
VALVE
TO NEXTVALVE
FROMPUMP
RESOLVERS
LOADER TILT CONTROL VALVEHOLD
PILOTPASSAGE
HEADEND
RODEND
STMG 746 - 97 -10/02
• Parallel lift inREGENERATIVEDUMP
70
The force of gravity tends to cause implements to lower faster than thehydraulic pump and makeup valves can fill the cylinders. A"REGENERATIVE DUMP" position can reduce this tendency.
Due to the lands of the tilt valve, return oil from Port "B" cannot go to thetank. The return oil from the implement is instead directed through thebridge passage to Port "A" when the control spool is shifted to theREGENERATIVE DUMP position.
This position allows the bucket to be powered down by pump flow. Thisaction prevents cylinder cavitation and causes the bucket to dump faster.
LINE RELIEF ANDMAKEUP VALVE
FLOW CONTROLVALVE
CONTROLSPOOL
FROMPREVIOUS
VALVE
TO NEXTVALVE
PORTB
PORTA
FROMPUMP
RESOLVERS
PILOTPASSAGE
LOADER TILT CONTROL VALVEREGENERATIVE DUMP
STMG 746 - 98 -10/02
• Loader auxiliarycontrol valve in HOLD:
- Solenoids controlledby the AuxiliaryControl Module(ECM)
71
The loader auxiliary control valve is equipped with two proportionalsolenoids.
The solenoids direct pilot oil to shift the control spool. The solenoids arecontrolled by the Auxiliary Control Module (ECM).
LINE RELIEF ANDMAKEUP VALVE
FLOW CONTROLVALVE
CONTROLSPOOL
TO NEXTVALVE
PORTB
PORTA
FROMPUMP
RESOLVERS
AUXILIARY HYDRAULICSOLENOID VALVE NO. 1
FROMLOADER
JOYSTICK
LOADER AUXILIARY CONTROL VALVEHOLD
AUXILIARY HYDRAULICSOLENOID VALVE NO. 2
STMG 746 - 99 -10/02
• Loader auxiliarycircuit:
- Quick coupler switch
- Continuous flowswitch
- Quick couplersolenoid valve
- Auxiliary ControlECM
- Auxiliary hydraulicsolenoids
72
The Auxiliary Control ECM receives inputs from the thumb switch on thejoystick, the continuous flow switch and the quick coupler switch.
The Auxiliary Control ECM senses the position of the quick couplerswitch to control the quick coupler solenoid valve. The solenoid valvelocks or unlocks the coupler pins.
A manual diverter valve (not shown) mounted on the loader linkageallows oil to and from the coupler pins or to and from an auxiliary circuit.
When the coupler pins are unlocked, the coupler pins can be engaged ordisengaged with the quick coupler switch. The thumb switch can be usedto engage the pins.
When the coupler switch is moved to the LOCKED position, theAuxiliary Control ECM will de-energize the quick coupler solenoid valve.The coupler pins are then locked in position.
G943 BU
REVERSE DIRECTIONDISABLE JUMPER
QUICK COUPLERSWITCH
2
5
1
3
4
6
LINE RELIEF ANDMAKEUP VALVE
FLOW CONTROLVALVE
CONTROLSPOOL
TO NEXTVALVE
PORTB
PORTA
FROMPUMP
RESOLVERS
CONTINUOUSFLOW SWITCH
H833 PU
203 BK
585 YL
586 BR
M968 BU
PILOT LOADERHANDLE
CONTROL
163 WH
779 WH
TO KEY SWITCH
TO KEY SWITCH
163 WH
N997 WH
AUXILIARYCONTROL
ECM
PILOT OIL FROMEND COVER
E544 GN
E540 PK
E543 WH
E540 PK
LOADER AUXILIARY CONTROL VALVEHOLD
203 BK
AUXILIARY HYDRAULICSOLENOID NO. 1
AUXILIARY HYDRAULICSOLENOID NO. 2
JOYSTICK
FROMLOADER
JOYSTICK
QUICK COUPLERSOLENOID VALVE
STMG 746 - 100 -10/02
• Loader auxiliarycircuit:
- Auxiliary ControlECM sensed thumbswitch position tocontrol auxiliarysolenoid
- Continuous flowswitch used tomaintain flow rate
- Reverse directiondisable jumper
73
When the thumb switch on the joystick is moved, the Auxiliary ControlECM senses the position of the thumb switch and send a variable currentto one of the proportional solenoids to shift the auxiliary control spool.The current will vary depending on how far the thumb switch is moved.The solenoid directs pilot oil to one end of the control spool.
Operation of the flow control spool and resolvers is the same as with otherpressure compensated implement control valves used on backhoe loaders.
If the operator wants to maintain a fixed flow rate, the continuous flowswitch can be pressed momentarily. Then release the thumb switch withinone second. When the thumb switch is released, the desired flow rate willbe maintained until either the thumb switch is moved, the continuous flowswitch is pressed again or the quick coupler switch is activated.
For some attachments (broom), the reverse direction disable jumper isinstalled to disable solenoid No. 1. The auxiliary circuit will now onlyoperate in one direction.
QUICK COUPLERSWITCH
2
5
1
3
4
6
LINE RELIEF ANDMAKEUP VALVE
FLOW CONTROLVALVE
CONTROLSPOOL
TO NEXTVALVE
PORTB
PORTA
FROMPUMP
RESOLVERS
FROMLOADER
JOYSTICK
CONTINUOUSFLOW SWITCH
H833 PU
203 BK
585 YL
586 BR
M968 BU
QUICK COUPLERSOLENOID VALVE163 WH
779 WH
TO KEY SWITCH
TO KEY SWITCH
163 WH
N997 WH
AUXILIARYCONTROL
ECM
PILOT OIL FROMEND COVER
E544 GN
E540 PKE543 WHE540 PK
LOADER AUXILIARY CONTROL VALVESHIFT
203 BK
AUXILIARY HYDRAULICSOLENOID NO. 1
AUXILIARY HYDRAULICSOLENOID NO. 2
JOYSTICK
G943 BU
REVERSE DIRECTIONDISABLE JUMPER
PILOT LOADERHANDLE
CONTROL
STMG 746 - 101 -10/02
74
• Loader pilot controls:
1. Pilot joystick
2. Buttons
3. Thumb switch
On the loader pilot joystick (1), the yellow buttons (2) on the control canbe used to control an auxiliary function or for AWS. On the electricalschematic the buttons control the left and right broom angle relays.
The thumb switch (3) works with a the Auxiliary Control ECM to varythe current to two proportional solenoids mounted on the loader auxiliaryvalve. A switch on the front of the joystick is used to downshift thetransmission or neutralize it depending on how long the switch is held.
1
2
3
STMG 746 - 102 -10/02
75
• Auxiliary Control ECM(arrow)
The Auxiliary Control ECM (arrow) is located below the side consolegauge and switch panel.
If the machine is equipped with the optional Machine Security System(MSS), the ECM for MSS is attached to the back of the Auxiliary ControlECM.
STMG 746 - 103 -10/02
76
• Loader components:
1. Coupler cylinderguard
2. Diverter valve lever
3. Reverse directiondisable harnessconnector
The diverter valve lever (2) allows the operator to divert flow to anattachment and blocks the oil in the coupler cylinder to lock theattachment to the loader linkage. The cylinder is protected by a guard (1).
The reverse direction disable harness connector (3) permits connecting ajumper to disable the No. 1 auxiliary solenoid to allow flow in only onedirection.
When the jumper (not shown) is installed, the thumb switch on the loaderjoystick only operates an attachment in one direction.
An additional harness connector (not shown) allows the connection of anelectrically controlled function to the front loader. This function iscontrolled by the two yellow buttons shown earlier on the loader joystick.
12
3
STMG 746 - 104 -10/02
• Ride Control System:
- Standardtransmission
77
This illustration shows a combined electrical/hydraulic schematic of theRide Control System on machines with a standard transmission. The liftcontrol valve is in HOLD and is blocking both the rod and head ends ofthe cylinder.
When the key start switch is in the ON position, power is available at theride control switch through the 614-PU wire and the switch and dashindicators are illuminated. When the ride control switch is in the OFFposition, the ride control solenoid is not energized.
To energize the coil in the ride control relay the pressure switch must beclosed to complete the circuit from the ride control switch.
The pressure switch senses the pressure in the line to the rod end of theloader lift cylinder. When the pressure in the rod end of the loader liftcylinder is less than the actuation pressure of the pressure switch, theswitch closes.
PUMPSUPPLY
SIGNAL FROMPREVIOUS VALVE
FLOWCOMPENSATOR
LIFT CONTROL VALVE
RESOLVERS
PRESSURESWITCH
12
976-OR
RIDE CONTROLSWITCH
RIDE CONTROLRELAY
RIDE CONTROLSTANDARD TRANSMISSION
ON
ARCSUPPRESSION
614-PU
134-YL
123456
A972-OR
975-WH
F738-WH
PUMPSUPPLY
LIFTCYLINDERS
F739-GN
SOLENOIDCHECKVALVE
SHUTOFF VALVE
12
M969-YL
TO TANK
ACCUMULATOR
E701-PK
F748-WH
ORIFICE
ORIFICE
➥
• Ride control switchON:
- Circuit groundedthrough closedpressure switch
- Pressure switchsenses rod endpressure
STMG 746 - 105 -10/02
When the pressure switch is closed, the coil in the relay is energized,closing the relay. Power from the ride control switch flows through theride control relay to the solenoid. The ride control solenoid is nowenergized.
When the ride control solenoid is energized, pump supply oil flowsthrough the solenoid to unseat the check valve and to shift the shut-offvalve. This action connects the head end of the loader lift cylinders to theride control accumulator and the rod end of the loader lift cylinders areopen to the tank through the check valve.
When the machine is driven over rough terrain with the ride controlsystem ON, the loader lift cylinders extend and retract. As the liftcylinders extend, oil displaced from the rod ends of the cylinders open tothe tank and oil which is stored in the accumulator flows into the headends of the cylinders. As the lift cylinders retract, oil displaced from thehead ends of the cylinders flows into the accumulator, and oil is drawnfrom the tank into the rod ends of the cylinders. The accumulator acts asa shock absorber when the cylinders retract, providing a smoother ride.
When the ride control system is OFF, the ride control solenoid is notenergized. Under this condition, the solenoid drains the supply oil to thecheck valve and the shutoff valve to the tank. The check valve seats andblocks the passage from the rod ends of the lift cylinders to the tank. Theshut-off valve moves down and blocks the flow of oil through it. Theorifice dampens the closing of the check valve and the shifting of theshut-off valve.
The orifice in the line between the accumulator and cylinder head endsprevents the rapid loss of the oil which is stored in the accumulator whenthe loader arms are lowered. The orifice also allows the accumulator tobe charged, without adversely affecting machine performance when theloader arms are lifted.
The pressure switch prevents the ride control relay, and therefore, the ridecontrol solenoid, from energizing if the pressure in the rod end of theloader lift cylinder becomes greater than the actuation pressure of thepressure switch. An example of this situation is when the loader arms areused to lift the front wheels off of the ground. If the ride control systemwas engaged under this circumstance, the machine would fall to theground.
- Low pressure,switch closes
- Relay closes
- Ride controlsolenoidenergized
• Ride control ON:
- Accumulator andcylinder head endsconnected
- Accumulator acts asshock absorber overrough terrain
• Ride control OFF:
- Solenoid notenergized
- Orifice createsrestriction betweenaccumulator andcylinders
- Prevents rapidloss of stored oil
- Allowsaccumulator to berecharged
• Pressure switch
- Prevents ride controlfrom being activatedif pressure high
STMG 746 - 106 -10/02
• Ride Control System:
- Power shifttransmission
78
The Ride Control System on machines with the optional autoshifttransmission use the Autoshift ECM. The Autoshift ECM monitors theposition of the ride control switch and determines when to operate the ridecontrol system.
The ride control switch is a three position switch: OFF, ON and AUTO.
When the key start switch is in the ON position, power is available at theride control switch through the 614-PU wire and at the Autoshift ECMthrough the 123-WH wire. The Autoshift ECM monitors the ride controlswitch position at terminals 21 and 22. When the ride control switch is inthe OFF position, the circuits at terminals 21 and 22 of the Autoshift ECMare open.
PUMPSUPPLY
SIGNAL FROMPREVIOUS VALVE
FLOWCOMPENSATOR
LIFT CONTROL VALVE
RESOLVERS
PRESSURESWITCH
976-OR
RIDE CONTROLSWITCH
RIDE CONTROLRELAY
RIDE CONTROLAUTOSHIFT TRANSMISSION
AUTO MODE ON
ARCSUPPRESSION
134-YL
123456
A972-OR
975-WH
F738-WH
PUMPSUPPLY LIFT
CYLINDERS
F739-GN
SOLENOIDCHECKVALVE
SHUTOFF VALVE
12
M969-YL
TO TANK
ACCUMULATOR
E701-PK
F748-WH
212239372318
R/C AUTO SW TO GNDR/C ON SW TO GNDSOL RETURNRIDE CNTRL RELAYPRESS SW TO GNDR/C ENABLE CMD SW TO BAT
AUTOSHIFT ECM
E702-OR12
12
BATTERYGROUND
123-WH
12
614-PU
➥
STMG 746 - 107 -10/02
When the ride control switch is in the ON position, power transfers to theride control relay. Power available at the ride control switch illuminatesthe indicators in the switch and the ride control indicator on theinstrument panel.
With the ride control switch closed, the Autoshift ECM reads a closedcircuit at terminal 22 (Ride Control ON). This closed circuit confirms tothe Autoshift ECM that the ride control switch is in the ON position.
Before the Autoshift ECM will create an output signal to energize the ridecontrol solenoid, the condition of the pressure switch which is located inthe rod end of the loader lift cylinder must be determined. The pressureswitch senses rod end cylinder pressure. If the rod end pressure is belowthe actuation setting of the switch, the switch is closed and the AutoshiftECM will send a signal to close the ride control relay. When the relaycloses the solenoid is energized. If the pressure is too high the switch isopen and the Autoshift ECM will not send a signal to the relay.
When the ride control solenoid is energized, pump supply oil flowsthrough the solenoid to unseat the check valve and to shift the shut-offvalve. This action connects the head end of the loader lift cylinders to theride control accumulator, and the rod end of the loader lift cylinders areopen to the tank through the check valve.
When the ride control switch is in the AUTO position the Autoshift ECMreads a closed circuit at terminal 21.
A closed circuit at terminal 21 confirms to the Autoshift ECM that theride control switch is in the AUTO position. Under this condition, theAutoshift ECM uses input from the pressure switch and the speed sensorto determine when to operate the ride control system.
If the speed sensor input indicates ground speed is less thanapproximately 9.5 kilometers per hour (6 mph), the Autoshift ECM willnot engage the ride control system. If the input indicates that the groundspeed is greater than approximately 9.5 kilometers per hour (6 mph), theAutoshift ECM directs an output signal to close the ride control relay.
When the relay closes the solenoid is energized.
NOTE: ET can be used to adjust the speed at which the AutoshiftECM engages Ride Control.
• Ride control switchON:
- If Autoshift ECMsenses:
- Circuit at terminal22 closed
- Pressure switchclosed
- Then ride controlrelay closes:
- Ride controlsolenoidenergized
• Ride control switchAUTO:
- If Autoshift ECMsenses:
- Circuit at terminal21 closed
- Pressure switchclosed
- Sufficient groundspeed
- Then ride controlrelay closes:
- Ride controlsolenoidenergized
STMG 746 - 108 -10/02
79
• Ride Control Systemcomponents:
1. Ride control valve
2. Accumulator
3. Guard
The ride control valve (1) is located on the inside of the right frame railbelow the cab.
The accumulator (2) is protected by a guard (3).
12
3
STMG 746 - 109 -10/02
• Dead engine lowerwith loader lockvalves
80
Some machines may be equipped with optional loader lock solenoidvalves.
For these machines a dead engine lower switch is required to energize thesolenoids to allow the operator to lower the loader arms with a deadengine.
The dual function ride control switch is used with machines equipped withride control and the loader lock valves. When ride control is activated thelock valves solenoids are energized to allow ride control to work.
12
RD-18BR-18
12
RD-18BR-18
1234
12
12
12
1234
1234
1234
1234
YL-18GN-18YL-18
GN-18
ABC
BK-18GN-18BK-18
BU-18RD-18BK-18
ABC
BU-18RD-18BK-18
GN-18
BK-18GN-18BK-18
YL-18GN-18
GN-18
GN-18
BK-18
BK-18
PK-18PK-18
GN-18
BK-18
BK-18
OR-18YL-18BK-18BU-18
85 86
87
87A
30
YL-18
BK-18
85 86
87
87A
30
BK-18
YL-18
YL-18
YL-18
123456
BK-18
YL-18BK-18
GN-18
WH-18OR-18PK-18
GN-18BK-18YL-18
GN-18WH-18PK-18
OR-18YL-18BK-18
7 8
1
34
6
2
5
MOM
MOM
OR-18OR-18
BK-18
BK-18
YL-18
7 81
3
46
2
5 MOM
PU-18PU-18PU-18
CONN. 12 CONN. 12
CONN. 56
CONN. 19 CONN. 19
DEL. ARC SUPPR. 1
DEAD ENG LOWERCOMMAND RELAY
DEAD ENG. LOWER SW.
DEL. ARC SUPPR. 2
CONN. 57
DEAD ENG. LOWERENABLE RELAY
DUAL FUNCTION RIDECONTROL SWITCH
FLOAT DETENTPILOT PRESS. SW.
FLOAT DETENT LIMIT SW.
RH LOCK VALVE SOL.
LH LOCK VALVE SOL.
DEAD ENGINE LOWER CIRCUITSOLENOIDS ENERGIZED
STMG 746 - 110 -10/02
• Backhoe valve group:
- Mechanicallycontrolled
81
Backhoe Valve Groups
The following seven illustrations will cover the valves in the backhoevalve group that are mechanically operated.
All of the valves are closed-center. Only the swing, E-stick and auxiliaryvalves are pressure compensated.
SMU
LIFT
TILT
AUX
STEER
STICK
ENDCOVER
SWING
E-STICK
PUMP
TANK
BOOM
BUCKET
INLETMANIFOLD
AUX
LEFTSTABILIZER
RIGHTSTABILIZER
MANIFOLD
BACK FLOWCHECKVALVE
COOLER
SIDESHIFTLOCK PISTONS
LEVER
LEVER
"D" SERIES MECHANICALLY CONTROLLED BACKHOE VALVES
STMG 746 - 111 -10/02
• Backhoe auxiliarycontrol valve in HOLD:
- Pressurecompensated
- Three position spool
82
The auxiliary valve shown here is used for the extendible stick or can beused for other backhoe attachments.
These valves are controlled by foot pedals and are found in both themechanical operated backhoe valve group and in the pilot operatedbackhoe valve group.
The major components of these optional valves are the same as those inthe auxiliary valve in the loader section, except these valves do not have apilot operated line relief and makeup valve.
FROMPREVIOUS
VALVE
FROM PUMP
TO NEXTVALVE
PORTA
PORTB
PLUG
FLOW CONTROLVALVE
BACKHOE AUXILIARY CONTROL VALVEHOLD
• Stick control valve inHOLD:
- Mechanicallycontrolled
The stick control valve is equipped with a line relief valve for the rod endand a combination line relief and makeup valve for the head end. Thevalve is not pressure compensated.
The load check valve is not the same as used on the "C" Series. The loadcheck valve still serves the same function of preventing implement driftuntil system pressure increases to move the spool to the left to provideflow to the cylinder.
Due to improved control spool design, an advance signal passage is nolonger required for STICK OUT.
TO NEXTVALVE
LINE RELIEF ANDMAKEUP VALVE
LOAD CHECKVALVE
CONTROLSPOOL
FROMPREVIOUS
VALVE
HEADEND
RODEND
FROMPUMP
RESOLVERSLINE RELIEF
VALVE
STICK CONTROL VALVEHOLD
STMG 746 - 112 -10/02
83
STMG 746 - 113 -10/02
• Stick control valve inSTICK OUT
84
When an implement is activated and supply pressure is higher thancylinder pressure, the check valve is pushed to the left. Oil can then flowto the cylinder.
As long as the system pressure is higher than the work port pressure, theload check valve will stay to the right.
TO NEXTVALVE
LINE RELIEF ANDMAKEUP VALVE
LOAD CHECKVALVE
CONTROLSPOOL
FROMPREVIOUS
VALVE
HEADEND
RODEND
FROMPUMP
RESOLVERSLINE RELIEF
VALVE
STICK CONTROL VALVESTICK OUT
• Bucket control valvein HOLD:
- Mechanicallycontrolled
LINE RELIEF
LOAD CHECKVALVE
CONTROLSPOOL
FROMPREVIOUS
VALVE
TO NEXTVALVE
HEADEND
RODEND
FROMPUMP
RESOLVERS
BUCKET CONTROL VALVEHOLD
The bucket control valve contains line relief valves for the rod end and thehead end of the cylinder. The valve is not pressure compensated.
STMG 746 - 114 -10/02
85
LINE RELIEFVALVE
FLOW CONTROLVALVE
CONTROLSPOOL
FROMPREVIOUS
VALVE
TO NEXTVALVE
SWINGRIGHT
SWINGLEFT
FROMPUMP
RESOLVERS
SIGNALMETERING
SLOT
ADVANCESIGNAL
PASSAGE
CHECKVALVE
SWING CONTROL VALVEHOLD
To improve swing modulation, advance signal metering slots aremachined in the main control spool.
Inside the main control spool are two check valves. The spool also hasadvance signal passages. Inside the flow control spool is a load checkvalve which prevents swing drift.
The check valves allow the system to maintain pressure on the cylinderpistons in HOLD. Due to the check valves, the main control spool is nolonger a true closed-center control valve.
By maintaining a pressure on both sides of the cylinder pistons during aswing, the amount of swing "wag" is reduced when the swing lever isreturned to HOLD.
The check valves will also act as makeup valves to prevent cylindervoiding.
• Swing control valve inHOLD:
- Signal meteringslots improvemodulation
STMG 746 - 115 -10/02
86
• Check valves:
- Maintain pressure oncylinder pistons inhold
- Reduce swing "wag"
➥
STMG 746 - 116 -10/02
• Advance signaloperation
When the engine is not running, the springs (only one spring shown forclarity) at the left end of the flow control spool shift the spool to the right.
The flow control valve is in a parallel circuit and has equal access topump supply oil. When the engine is started, supply oil to the flowcontrol spool enters the passage in the center of the spool and fills thechamber at the right end of the spool. As pressure increases on the rightend of the flow control spool, the spool moves to the left against thesprings. Supply oil then flows to the main control spool where a smallamount of oil flows past both check valves in the main control spool andenters both work ports. The oil is then blocked by the cylinder pistons.This action maintains pressure on both ends of each piston.
As the flow control spool moves to the left, the metering slots in the flowcontrol spool begin to close creating a restriction to the pump supply oil.Because of the restriction, pressure in the work ports and on the right endof the flow control spool is reduced. The pressure on the right end of theflow control spool, which is limited by the flow control springs, is thesame as the pressure in the work ports. This pressure of 415 kPa (60 psi)is maintained in the work ports to improve the implement response whenthe main control spool is shifted.
When the spool is initially shifted, the advance signal passage sends somepump supply oil to the signal cavity before oil is directed to the cylinders.The signal is then sent back to the pump control valve to upstroke thepump. The signal metering slots meter some of this signal pressure to thetank, thus preventing the pump from going to a "high pressure standby"mode.
The signal metering slots provide more benefit to the operator when thespool is returned to the HOLD position. The slots meter the signalpressure to the tank and dampen the shock created by closing the spool.Operation of the swing is smoother and swing "wag" is further reduced.The signal metering slots also provide improved start-up metering.
NOTE: A signal limiter was shown in the first verion of this ServiceTraining Meeting Guide and other service literature. The limiter wasremoved just prior to first ship and is no longer used on the swingcircuit for any "D" Series machine.
• Swing RIGHT:
- Supply oil unseatsleft check valve
- Return oil unseatsleft check valve
- Left check valveprovides apressurized swing
When the spool is shifted to SWING RIGHT, the work port pressure issent through the signal network and to the flow control valve. Supply oilenters the main control spool and unseats the check valve on the right.Return oil from the swing right work port also enters the spool, unseatsthe right check valve, and flows to the tank. The left check valve creates aback pressure on the oil returning to the tank to provide a pressurizedswing.
Pressure oil on the right end of the flow control valve will work againstthe signal oil and springs on the left end of the flow control valve tomaintain the desired flow rate to the swing circuit.
LINE RELIEFVALVE
FLOW CONTROLVALVE
CONTROLSPOOL
FROMPREVIOUS
VALVE
TO NEXTVALVE
SWINGRIGHT
SWINGLEFT
FROMPUMP
RESOLVERS
SIGNALMETERING
SLOT
ADVANCESIGNAL
PASSAGE
CHECKVALVE
SWING CONTROL VALVESWING RIGHT
STMG 746 - 117 -10/02
87
• Boom control valve inHOLD:
- Mechanicallycontrolled
LINE RELIEF ANDMAKEUP VALVE
LOAD CHECKVALVE
CONTROLSPOOL
FROMPREVIOUS
VALVE
TO NEXTVALVE
HEADEND
RODEND
FROMPUMP
RESOLVERS
428D / 438D BOOM CONTROL VALVEHOLD
The boom control valve contains combination line relief and makeupvalves for the head end and rod end of the cylinder.
The valve is not pressure compensated. The load check valve preventsimplement drift whenever a circuit is first activated or due to lack of flow,the system pressure is less than needed to support or move the load.
Due to improved control spool design, an advance signal passage is nolonger required for BOOM-UP on the 428D and 438D.
On the 416D and 424D an advance signal passage is required.
NOTE: Due to the improved line routings, the head end and rod endworkports have been reversed on the "D" Series from the "C" Serieson the boom and stick circuits.
STMG 746 - 118 -10/02
88
STMG 746 - 119 -10/02
• Pilot operatedbackhoe valve group
• Stabilizer valves
• Sideshift frame
89
The following 12 illustrations are related to the pilot operated backhoesection valves, stabilizer valves and sideshift frame.
All of the valves are closed-center. Only the swing, E-stick and auxiliaryvalves are pressure compensated.
JOYSTICK
LEVER
JOY
ST
ICK
SMU
LIFT
TILT
AUX
STEER
STICK
ENDCOVER
SWING
E-STICK
PUMP
TANK
BOOM
BUCKET
INLETMANIFOLD
AUX
LEFTSTABILIZER
RIGHTSTABILIZER
MANIFOLD
JOY
ST
ICK
LEVER
PILOTSHUTOFF
RIDECONTROL
BACK FLOWCHECKVALVE
COOLER
SIDESHIFTLOCK
CYLINDERS
PA
TT
ER
N C
HA
NG
ER
"D" SERIES PILOT CONTROLLED BACKHOE VALVESAND STABILIZER VALVES
STMG 746 - 120 -10/02
90
• Backhoe valve group:
1. Boom
2. Swing
3. Bucket
4. Stick
5. E-Stick
This illustration shows the pilot operated backhoe valve group located atthe rear of the machine. Outlet ports to the cylinders face the rear of themachine on all models. This change from the "C" Series resulted inimproved line routing.
The valve group can have up to six valve sections.
Access to the secondary resolvers on center pivot machines must be donefrom below the machine instead of at the rear of the machine as was doneon former backhoes.
1
2
3
4
5
STMG 746 - 121 -10/02
91
• Hydrauliccomponents:
1. Optional patternchangeover valve
2. Pilot shutoff valve
3. Pilot returnmanifold
The optional pattern changeover valve (1) for the pilot operated backhoevalve group is mounted on the right side of the rear frame.
The valve allows the operator to change from the excavator pattern to thebackhoe pattern.
Machines equipped with pilot hydraulics are equipped with a backhoeshutoff switch on the side console. The switch controls the pilot shutoffsolenoid valve (2) that is mounted on the front of the rear axle.
The solenoid, when energized, allows pilot oil to flow to the joysticks.When the solenoid is de-energized the joysticks are disabled.
To lower implements with a dead engine, the key start switch must beturned to the ON position.
NOTE: The axles on the "D" Series no longer feature brake discinspection ports.
2
31
STMG 746 - 122 -10/02
• Stick control valve inHOLD:
- Pilot operated
92
The stick control valve is equipped with a line relief valve for the rod endand a combination line relief and makeup valve for the head end. Thevalve is not pressure compensated.
Except for being pilot controlled, the valve operation is the same as themechanically controlled stick control valve.
LINE RELIEF ANDMAKEUP VALVE
LOAD CHECKVALVE
CONTROLSPOOL
TO NEXTVALVE
HEADEND
FROMPUMP
RESOLVERS RODEND
FROMPREVIOUS
VALVE
PILOTPASSAGE
LINE RELIEFVALVE
STICK CONTROL VALVEHOLD
STMG 746 - 123 -10/02
• Bucket control valvein HOLD:
- Pilot operated
93
The bucket control valve contains line relief valves for the rod end and thehead end of the cylinder. The valve is not pressure compensated.
Except for being pilot controlled, the valve operation is the same as themechanically controlled bucket control valve.
LINE RELIEFVALVE
LOAD CHECKVALVE
CONTROLSPOOLTO NEXT
VALVE
HEADEND
FROMPUMP
RESOLVERS RODEND
FROMPREVIOUS
VALVE
PILOTPASSAGE
BUCKET CONTROL VALVEHOLD
STMG 746 - 124 -10/02
• Swing control valve inHOLD:
- Pilot operated
94
Except for being pilot controlled, the valve operation is the same as themechanically controlled swing control valve.
NOTE: A signal limiter was shown in the first verion of this ServiceTraining Meeting Guide and other service literature. The limiter wasremoved just prior to first ship and is no longer used on the swingcircuit for any "D" Series machine.
LINE RELIEFVALVE
FLOWCONTROL
VALVE
CONTROL SPOOL
FROMPREVIOUS
VALVE
TO NEXTVALVE
SWINGRIGHT
SWINGLEFT
FROMPUMP
RESOLVERS
PILOTPASSAGE
SIGNALMETERING
SLOT
ADVANCESIGNAL PASSAGE
CHECKVALVE
SWING CONTROL VALVEHOLD
STMG 746 - 125 -10/02
• Boom control valve inHOLD:
- Pilot operated
95
Except for being pilot controlled, the valve operation is the same as themechanically controlled boom control valve.
LINE RELIEF ANDMAKEUP VALVE
LOAD CHECKVALVE
CONTROLSPOOL
TO NEXTVALVE
HEADEND
FROMPUMP
RESOLVERS RODEND
FROMPREVIOUS
VALVE
PILOTPASSAGE
BOOM CONTROL VALVEHOLD
STMG 746 - 126 -10/02
96
• Sideshift machines:
1. Boom
2. Frame
3. Stabilizers
Sideshift machines feature a boom (1) that can be shifted to differentpositions along a frame (2).
Lock pistons (not shown) are used to lock the boom to the frame rails.
The stabilizers (3) are used to raise and lower the machine. Sideshift andcenter pivot machines use the same type of control valves to operate thestabilizers.
1
2
3
• Sideshift slide locksolenoid operation forENGAGED andRELEASED
RELEASED
SLIDERAIL
SLIDEBAR
PUMPSUPPLY
ENGAGED
SOLENOID
CHECKVALVE
SLIDE LOCKPISTON
PUMPSUPPLY
SIDESHIFT SLIDE LOCK SOLENOID VALVE
This schematic shows the sideshift slide lock solenoid and orifice checkvalve operation.
In the ENGAGED position, the solenoid is not energized. The solenoidblocks the system oil flow. Pump supply pressure can flow past the checkvalve to the slide lock pistons. The pistons clamp the stabilizer frameslide rails against the bolts on the slide bars to prevent slide framemovement.
The check valve will seat as shown to maintain pressure on the pistonswhen system pressure decreases.
In the RELEASED position, the solenoid is energized. The solenoidallows system supply oil to go to the tank. The slide lock pistons are nolonger pressurized. The slide bar can then move along the slide rail.
STMG 746 - 127 -10/02
97
STMG 746 - 128 -10/02
98
• Stabilizer circuitcomponents:
1. Stabilizer valvegroup
2. Pilot accumulator
3. Pilot pressure testport
The stabilizer valve group (1) and pilot accumulator (2) are mounted onthe inside of the rear frame on the right side of the machine.
The pilot accumulator provides dead engine implement loweringcapabilities.
The pilot accumulator is not used on the 416D, 424D, 428D and 438D.
The pressure test port (3) is used for checking pilot system pressure.
NOTE: All of the lines are not connected in this view. The line fromthe pilot accumulator is to be connected to the stabilizer valve group.
1
2
3
STMG 746 - 129 -10/02
• Stabilizer operation:
- Load check valves
- Pilot lock checkvalves
99
The stabilizer schematic shown is for machines equipped with mechanicalcontrols for the backhoe and loader valve groups. The left stabilizer is inHOLD and the right stabilizer is being SHIFTED.
The stabilizer cylinders are controlled by closed-center valves equippedwith lock check valve and pilot lock check valves.
The check valves prevent cylinder drift in either direction.
Pilot control valves are used to shift the stabilizer control spools.
Orifices and resolvers are used to signal the pump as to flow needs of thestabilizer circuits.
When a pilot control lever is shifted, pilot oil is sent to one side of thestabilizer control spool to shift it. As the spool shifts, some pilot oil isdirected to a pilot lock check valve.
PRESSUREREDUCING
VALVE
LEFTSTABILIZER
RIGHTSTABILIZER
SIGNAL FROMLOADER SECTION
SIGNAL TOBACKHOESECTION
FROM PUMP
LEFT PILOTLEVER
RESOLVER
ORIFICES
LOCK CHECKVALVES
PILOT LOCKCHECK VALVES
RIGHT PILOTLEVER
CHECKVALVE
RETURNMANIFOLD
416D / 424D / 428D / 438D BACKHOESTABILIZERS HYDRAULIC CIRCUIT
SHIFT RIGHT STABILIZER
➥
STMG 746 - 130 -10/02
When the pilot lock check valve shifts, blocked oil that was working withthe lock check valve spring to keep the lock check valve seated to preventcylinder drift is allowed to drain to the tank.
When this occurs, the lock check valve shifts opening one side of thestabilizer cylinder to the tank.
Pump supply oil from the stabilizer control spool now flows through theother lock check valve into one of the stabilizer cylinder ports to move thecylinder either up or down.
Also when the stabilizer control spool is shifted, some of the pump supplyoil also becomes signal oil to signal the pump.
When the pilot control lever is released, the spring in the pilot lock checkmoves to block oil from flowing to the tank through the check valve.This blocked oil works with the spring on the lock check valve to seat thelock check valves. Oil is now trapped in both sides of the stabilizercylinders. The stabilizer stay locked in position.
STMG 746 - 131 -10/02
• Stabilizer circuit forpilot controls:
- Pilot accumulator
- Pilot shutoffsolenoid
100
The stabilizer valves used on machines with pilot controls for the backhoeand loader operate the same as on machines with mechanical controls.
Machines equipped with pilot controls are also equipped with a pilotaccumulator to allow implement lowering capabilities with a dead engine.
The key start switch must be turned to the ON position to shift the pilotshutoff solenoid to allow pilot flow to the joysticks.
Refer to the Operation and Maintenance Manual for the respectivemachine for additional information on lowering the implements if theaccumulator has bled down.
TOJOYSTICKS
PRESSUREREDUCING
VALVE
LEFTSTABILIZER
RIGHTSTABILIZER
SIGNAL FROMLOADER SECTION
SIGNAL TOBACKHOESECTION
FROMPUMP
LEFT PILOTLEVER
PILOTACCUMULATOR
RESOLVER
ORIFICES
LOCK CHECKVALVES
PILOTSHUT OFF
PILOT LOCKCHECK VALVES
RIGHT PILOTLEVER
CHECKVALVE
RETURNMANIFOLD
420D / 430D / 432D / 442D BACKHOESTABILIZERS HYDRAULIC CIRCUIT
SHIFT RIGHT STABILIZER
STMG 746 - 132 -10/02
• Auto-up stabilizersystem
101
The auto-up stabilizer system is an option that allows the operator tomove the stabilizer pilot control lever into a solenoid detent position toraise the stabilizer.
The stabilizer up switches are located in the stabilizer control valve groupand are closed by the stabilizer pilot control lever.
The timer holds the control lever in the detent position for approximately10 seconds. After 10 seconds the stabilizers should be fully raised.
The stabilizer alarm advises operator that the stabilizers are down whenthe operator shifts the transmission out of NEUTRAL.
NOTE: The timer is activated the instant the stabilizer pilot controllever is moved. The timer starts before the lever is placed in thedetent position.
12
12
PU-18BK-18
PU-18BK-18
PU-18BK-18
PU-18BK-18
12
12
12
12
1234
1234
YL-18BK-18
YL-18BK-18
BAT(+)GND(-)INPUT(S)OUTPUT(L)
A-1B-2B-1C-1
BK-18PU-18YL-18
BU-18
BK-18
LEFT STAB. UP SW,
RIGHT STAB. UP SW.
L. STAB UP DETENT
R. STAB. UP DETENT
DETENT VALVE GP
CONN. 48
CONN. 48
STAB. TIMER
CONN. 12 CONN. 12
STAB. LEG UP DETENT
BK-18YL-18OR-18
12
12
12
PU-18BK-18
PU-18BK-18
BK-18
PU-18BK-18
PU-18BK-18
12
12
1234
OR-18PU-18
+-
YL-18BU-18
STAB. LEG ALARM
HORN ALARM
ALARM DIODE BLOCKCONN. 17
ALARM VALVE GP
LEFT STAB. UP SW.
RIGHT STAB. UP SW.
CONN. 48
CONN. 48
AUTO-UP STABILIZER SYSTEMTIMER ACTIVATED / SOLENOIDS ENERGIZED
STMG 746 - 133 -10/02
• All Wheel Steer
102
All Wheel Steer System (AWS)
The All Wheel Steer (AWS) system is similar to what was used on the "C"Series machines.
Operation of the AWS valve is the same. The major differences betweenthe models are:
- Since the "D" Series AWS system uses non-boosted brakes, asteering and brake resolver is no longer in the signal line betweenthe steering priority valve and the SMU.
- Due to the reverse signal network, the lines routing between thevalve sections has changed.
- The switch to control AWS has been changed to two separate buttonsas shown earlier.
TO BACKHOE VALVE GROUP
REARAXLE
FRONTAXLECROSSOVER
LINE RELIEFVALVES
STEERING METERING UNIT
STEERINGPRIORITY
VALVE
ALL WHEEL STEER SYSTEMHOLD
FROM STABILIZERVALVE GROUP
THERMALRELIEFVALVE
CIRCLESTEERVALVE
PILOTPOPPETVALVES
PILOTPOPPETVALVES
LOCKVALVE
TST 1 TST 2
RESOLVER
RESOLVER
IRMSHUTOFF
VALVE
IRMLEFT
VALVE
IRMRIGHTVALVE
TO BRAKE VALVE
ALL WHEEL STEERCONTROL VALVE
GROUP
LOADERVALVEGROUP LIFT
TILT
AUXILIARYBACK FLOW
CHECK VALVE
TO BACKHOEVALVE GROUP
RETURN
TO STABILIZERVALVE GROUP
SIGNAL
STMG 746 - 134 -10/02
• Machine SecuritySystem:
- Theft deterrent
- Uses CaterpillarElectronic Keys
- Machine SecurityControl (MSC)
103
OPTIONAL MACHINE SECURITY SYSTEM (MSS)
The Machine Security System (MSS) is a theft deterrent and reduces thechance of unwanted machine operation. MSS uses Caterpillar ElectronicKeys that have unique identification numbers. The MSS uses a MachineSecurity Control (MSC) with the keys. The MSC can be programmedwith the key ID's to restrict or allow access to the machine. No two keyshave the same ID and are not configurable. Electronic Technician is usedto program the MSC.
85 86
87
87A
30
1234
12
ABC
1234
ABC
ABC
PU-18
GN-18BK-18
GN-18BK-18
PU-18
GN-18PK-18
PK-14
PK-14PK-18 PK-18BK-18 BK-18GN-18 BU-18
OR-18YL-18RD-18
GN-18PK-18
RED
GREEN
12
RD-18
BK-18BK-18GN-18OR-18
PK-18
YL-18BU-18GN-18PU-18GN-18PK-18YL-18PK-18
OR-18BR-18
13579
111318192426293140424547525358606264666870
BATTERYGROUND
DRIVER NO. 2 OUTPUTEXCITER COIL SIGNAL LINE
DRIVER NO. 1 INPUTDRIVER NO. 1 OUTPUT
UNUSEDDRIVER NO. 2 INPUT
LED GROUNDKEY SWITCH ON POSITION INPUTALTERNATOR R TERMINAL INPUT
UNUSEDKEY SWITCH CRANK POSITION INPUT
UNUSEDCAT DATA LINK +CAT DATA LINK -
UNUSEDUNUSED
EXCITER COIL RETURN LINEDRIVER NO. 1 GROUND RETURN
RED LED SIGNAL LINEGREEN LED SIGNAL LINEDRIVER 2 ENABLE INPUT
UNUSEDUNUSEDUNUSED
RD-18BK-18BU-18YL-18PK-18GN-18
OR-18BK-18PK-18YL-18
OR-18
OR-18BR-18
PK-18PK-18PU-18GN-18GN-18
MACHINE SECURITY SYSTEMMACHINE OPERABLE
EXCITERCOIL
MSS ENGINERELAY
MSS LEDINDICATOR
CAT DATA LINK
MACHINE SECURITY CONTROL (MSC)
➥
STMG 746 - 135 -10/02
The exciter coil will read the ID of the key. The exciter coil is mountedaround the existing key start switch. The MSC will check the ID of thekey for the authorization. If the key is authorized by the MSC, themachine will operate normally. The MSS will keep critical machinefunctions disabled if the key does not match any authorized keys in theMSC.
The MSS LED indicator provides basic MSS information to the machineoperator. The green LED indicates the machine is operable, while the redLED indicates the machine is inoperable.
The MSS can be installed in one of two ways:
- Disabling power to two items that are currently on the machine.Solenoids and relays can be controlled with this method.
- Causing another ECM to disable a critical machine function unlessan authorized ID key is used.
To make modifications to the MSS, the technician must have a key withMaster Access Level for that MSS or a "factory password."
The factory password is determined from the following items: ProductID, Software Part Number from the Machine Security Control, SerialNumber from a registered version of ET and a tattletale. A factorypassword can be used one time.
104
• Conclusion
CONCLUSION
This presentation has provided an overall review of the steering andimplement hydraulic systems used in the "D" Series Backhoe Loaders.
When used in conjunction with the service manual, the information in thispackage should permit the serviceman to do a thorough job of analyzing aproblem in these systems.
For service repairs, adjustments and maintenance, always refer to theOwner and Operator Manual, Service Manuals and other related servicepublications.
STMG 746 - 136 -10/02
