Chapter 22 Bennet

8/10/2019 Chapter 22 Bennet

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Chapter 22

Driveshaft Assemblies


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Objectives (1 of 3)

Identify the components in a truck driveline.

Explain the procedures for inspecting,

lubricating, and replacing a universal joint.

Describe the various types of wear a

universal joint might experience.

Outline the procedure for sourcing chassis

vibration.


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Objectives (2 of 3)

Define and explain the importance of

phasing.

Explain the importance of driveline working

angles and how to calculate them.

Troubleshoot some typical driveline

complaints.

Describe the procedure for balancing adriveshaft.


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Objectives (3 of 3)

Describe the operation of a hydraulic

retarder.

Explain how an electric retarder operates.


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A Typical Truck Driveshaft


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Slip Joint


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Universal Joint


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A Stand Pipe

Ensures constant lubrication and prevents

dry startup.


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Bearing Cup with Needle Bearings


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Carrier Bearing


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Shop Talk

When replacing a hanger bearing, make sure

you look for and do not lose track of the shim

pack that is usually located between the

bearing mount and cross member. The shims set the driveshaft angles and

omitting them will result in a driveline

vibration.


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Parallel Arrangement


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Broken Back Arrangement


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Driveline Phasing


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Shop Talk

Clean grease fittings thoroughly to remove

accumulated grease and abrasives before

use.

Any contaminants on the zerk nozzle can beforced through the nipple into the bearing

during lubing.


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U-Joint Lube Schedule

See Table 222 on page 650 of the

textbook.


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Shop Talk

On-highway operation is generally defined as

an application that operates the vehicle

running less than 10 percent of total

operating time on gravel, dirt, or unimprovedroads.

Vehicles running more than 10 percent

operating time on poor road surfaces areclassified as off-highway in terms of

preventive maintenance.


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Warning

If grease is only seen to exit from three of the

four trunnion seals, the bearing is not

properly lubed and will almost certainly fail.

You must take the appropriate correctiveaction when U-joints fail to take grease.

If a driveshaft separates because of a U-joint

failure, it can take out air tanks, fuel tanks,and generally cause damage that greatly

exceeds the cost of replacing a single U-joint.


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How to Ensure Complete

Lubrication of the Slip Joint


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Caution

Half-round end yoke self-locking retaining

bolts should not be reused more than five

times.

If in doubt as to how many times bolts havebeen removed, replace with new bolts.


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Caution

When removing a driveshaft with half-round

or flange-type yokes, support the weight of

the driveshaft with a sling before separating

the U-joints.


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Caution

In cold temperatures, you should drive thevehicle immediately after lubricatingdriveshafts.

This activates the slip spline assembly andremoves excessive lubricant.

Excess lubricant in slip splines can freeze incold weather to a wax consistency and force

the breather plug out. This would expose theslip joint to contaminants and eventually resultin wear and seizure.


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Shop Talk

Before removing a driveshaft, mark the slip

yoke assembly and tube shaft with a paint

stick to ensure the correct phasing alignment

on reassembly. If the shaft assembly is to be cleaned before

reassembly, use a steel scribe to indent

alignment marks.


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Shop Talk

If only one end of the driveshaft requires service,

disconnect that end, unscrew the slip shaft seal

(dust cap) from the slip yoke assembly, and then

separate the driveshaft at the slip joint.

When removing the entire driveshaft, disassemble

one end at a time, laying the disconnected end on

the floor carefully.

When reassembling, be sure that the arrows ormarks on the shaft and slip joint are in line to keep

the driveshaft yokes in phase.


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Removing a U-Joint (1 of 2)


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Removing a U-Joint (2 of 2)


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Caution

If the bearing cap binds in the yoke bore,

gently tap with a ball peen hammer in the

center of the bearing cap.

Do not tap the outer edges of the bearing capbecause this could damage either the

bearing cup or the yoke.


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Caution

Once in use, bearing caps and their trunnions

should remain matched.

Also, never take assembly shortcuts by

installing only the new bearing caps on aused trunnion, as this will usually result in a

rapid failure.

Regard a U-joint cross, its four bearingassemblies, and mounting hardware as a unit

and replace as such.


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Caution

It makes sense to remove the grease fittings

when installing a driveshaft.

If they are knocked against the yoke, they tend

to shear. You can easily reinstall them afterthe driveshaft has been installed.


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Chassis Vibration Diagnosis Flowchart

See Table 223 on page 659 of the textbook.

C l l ti D i h ft


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Calculating Driveshaft

Operating Angles


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Checking Half-round Yoke Angles


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Driveshaft Troubleshooting Guide

See Table 224 on page 664 of the

textbook.


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Hydraulic Driveline Retarder


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Electric Retarder


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Summary (1 of 7)

The components of a driveshaft assembly includethe following:

Yoke

Universal joint

Slip spline

Hanger bearing

Propeller shaft(s)

The purpose of U-joints is to connect drivetraincomponents when allowing the driveshaft(s) to

operate at changing angles.

S


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Summary (2 of 7)

Two types of driveline arrangements areused to transmit torque to the drive axle

carriers: the parallel-joint type and the

nonparallel or broken-back driveshaft type. Because of U-joint action, when a drive yoke

turns at a constant rpm, the driveshaft speed

increases and decreases once per revolution.

This fluctuation in driveshaft speed requires

the U-joints to be in phase.

S


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Summary (3 of 7)

Driveline vibrations are caused by looseyokes, excessive driveshaft radial runout, slip

spline joint radial play, bent driveshaft tubing,

and failing U-joints. A U-joint puller should be used to separate a

universal joint from a yoke assembly.

Avoid using high impact tools such as sledgehammers, because driveshaft damage can

result.

S


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Summary (4 of 7)

After removing the U-joint cross and bearingcups from a yoke, inspect the yoke bores for

bore alignment, damage, and metal burrs.

Burrs can be removed with a rat tail or halfround file and emery cloth.

Measure the yoke bores for wear using a go-

no-go wear gauge and check yoke bore

alignment using a machined alignment bar.

S


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Summary (5 of 7)

When diagnosing driveline vibrations, itshould be noted that they often originate

elsewhere in the chassis.

An electronic inclinometer is the preferredinstrument for measuring driveline

component angles. A protractor also may be

used.


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S


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Summary (7 of 7)

Electric driveline retarders operate byabsorbing the energy of motion by converting

it first to electrical energy using an eddy

current principle, and then dissipating it asheat.

Both hydraulic and electric driveline retarder

operation can be electronically controlled.

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Chapter 22 Bennet