Chapter 1

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Chapter 1Drive Shaft Assembly

Construction and Operation

Chapter 12


Objectives

Explain the purpose of a drive shaft assembly.

List the major parts of a typical drive shaft assembly.

Explain the function and operation of a slip yoke.

Explain the function and operation of a universal joint.


Objectives

Name and describe different types of universal joints.Discuss Hotchkiss drive and torque-tube drive.Describe the function of a center support bearing in a two-piece drive shaft.Briefly explain the concept of drive shaft assembly angles.


Drive Shaft Assembly

Drive shaft assembly (driveline) transfers power between transmission and rear axle assembly

Drive shaft assembly consists of:Slip yoke

Front universal joint

Drive shaft

Rear universal joint


Drive Shaft Assembly (Cont.)

(General Motors)



Slip yoke connects to transmission output shaft

Rear universal joint connects to differential through differential pinion yoke or flange

Balance weights reduce vibration



(Ford)



Drive shafts come in many sizes

Length is measured from center of each yoke hole on drive shaft ends

(General Motors)



On late-model vehicles, front and rear axles move to keep chassis level

On rear-wheel drives, rear axle housing and both rear wheels move up and down in relation to chassis

Suspension system connects rear axle assembly to chassis



Drive shaft angle and length must change to compensate for rear axle assembly movement

Flexible joints allow drive shaft assembly to flex or bend as rear axle assembly moves


Drive Shaft Assembly Power Flow

Transmission to slip yoke

Slip yoke to front universal joint and into drive shaft

Drive shaft into rear universal joint

Rear universal joint into rear axle assembly


Drive Shaft

Drive shaft, or propeller shaft, is central part of drive shaft assembly

Universal joints and other parts are attached to it

Drive shaft consists of steel tube with yokes welded or pressed on each end

Shaft is balanced when manufactured


Slip Yoke

Slip yokeUsed where drive shaft assembly enters rear of transmission

Slides on transmission output shaft whenever rear axle assembly moves

(Ford)


Slip Yoke (Cont.)

Steel tube with yoke at one end

Yoke attaches to front universal joint

Internal part of tube is splined

May have damper (weight) to absorb vibration (Ford)


Universal Joints

Universal joints (U-joints) are swivel connections, or couplings, that allow drive shaft assembly to transmit power smoothly and constantly

Two basic types:Cross-and-roller

Constant-velocity


Cross-and-Roller U-Joints

Cross-and-roller U-jointUsed on most rear-wheel drives

Sometimes called Cardan U-joint or conventional U-joint


Cross-and-Roller U-Joints (Cont.)

Center cross (spider)

Four cups containing needle bearings

Cups are machined to fit into:

Drive shaft yokes

Slip yoke

Differential pinion yoke

Cup seals keep grease in cup and prevent entry of dirt and water

(General Motors)



(General Motors)



Some U-joints can be greased

Some U-joints are sealed at factory and cannot be greased unless disassembled

(Chrysler)



Cups may be held in yokes in different ways

(Dana)



Some vehicles use injected plastic to hold cups in place

(Dana)



Larger vehicles may use more complex U-joints

(ArvinMeritor)



Conventional U-joint is almost always driving at an angle, causing drive shaft speed to rise and fall twice for every revolution

Range of speed fluctuation increases as joint angle increases



Fluctuation in drive shaft speedCreated at front U-jointCanceled at differential pinion yoke by rear U-joint

When equal angles are formed by U-joint at transmission and drive shaft and U-joint at drive shaft and rear axle

Canceled if U-joints are aligned in phase


CV Joints

Constant-velocity U-joints (CV joints)Provide extremely smooth power transfer

Are more complicated than conventional U-joints

Are used by larger rear-wheel drive vehicles to further reduce vibration


CV Joints (Cont.)

Double Cardan U-joint

Vibration forces are cancelled within center yoke

(General Motors)


CV Joints (Cont.)

Ball-and-trunnion U-jointNot used on modern vehicles

Separate slip yoke not needed


CV Joints (Cont.)

Rzeppa jointBall bearings held by slotted cross assemblyBall bearings move up and down on cross as torque is transmitted through themTransmits power through changing angles

(Dana)


CV Joints (Cont.)

Tripod jointResembles ball-and-trunnion U-joint, but uses three-pointed cross pin

Often used as inner bearing on front-wheel drives

Sometimes used on drive axles of rear-wheel drives with independent rear suspension


Differential Pinion Yoke

Differential pinion yokeConnects to drive pinion gear in rear axle assembly

Has internal splines that fit external splines on drive pinion gear shaft

Held to shaft by large locknut


Differential Pinion Yoke (Cont.)

Differential pinion flange, or companion flange

Two-piece yoke joined by mating flanges

One flange holds rear U-joint, other connects to pinion gear

(Ford)


Classes of Drive Shaft Assemblies

Hotchkiss driveUsed almost exclusively in late-model, rear-wheel vehicles

Torque-tube driveUsed on some makes of vehicles for many years, but now uncommon


Hotchkiss Drive

Hotchkiss driveUsed with rear leaf springs

Salsbury driveUsed with coil springs

(Fiat)


Hotchkiss Drive (Cont.)

Variation of Hotchkiss drive:Constant-velocity U-joint is usedSlip yoke is at rear of shaftOne spline is larger than others

(Ford)


Torque-Tube Drive

Torque-tube drive is designed to control rear-end torque

Drive shaft connects to transmission output shaft through U-joint

Other end of shaft connects to drive pinion gear through coupling or splined connection

U-joint at only one end


Torque-Tube Drive (Cont.)

Drive shaft assembly can flex only at U-joint between transmission and drive shaft

Rear axle assembly moves up and down in arc as it pivots about U-joint

Distance between transmission and rear axle assembly is always the same, so no slip yoke is needed


Two-Piece Drive Shaft

Two-piece drive shaft Two drive shafts• Steel tubes with yokes on all four ends

Three universal joints• Identical to those on one-piece drive shaft

Drive shaft assembly angles are reduced at each U-joint, reducing vibration


Two-Piece Drive Shaft (Cont.)



Center support bearing keeps drive shafts aligned

Slip yoke usually installed behind support bearing

Some designs have two slip yokes

(Fiat)



Two-piece drive shafts:Were used when vehicle frame design prevented use of single drive shaft

Were discontinued during 60s and 70s except on large trucks and some long-bed pickups

Became common again with increased popularity of large SUVs


Drive Shaft Assembly Angles

All rotating parts have axial centerline, or rotational axis

When rotating parts are coupled together, centerlines must be closely matched


Drive Shaft Assembly Angles (Cont.)

Perfect alignment is seldom achieved



Drive shaft assembly angle (also called operating angle or U-joint angle)



On front-engine, rear-wheel drive vehicles, drive shaft assembly angle exists between centerlines of:

Transmission output shaft and drive shaft

Drive shaft and drive pinion gear shaft



Angles are measured at front and rear U-joints

Manufacturer’s specification is usually about 1° or 2°

If angle is greater than specified:Speed fluctuations of shaft tube increase

Shaft may have objectionable vibration

Joint can break



Angles are affected by:Added weight to vehicle

Road surface condition

Vehicle acceleration or deceleration

Suspension system wear or alterations

Original angles must be kept as close as possible to specifications


Review Questions

To compensate for rear axle movement, the driveshaft ___ and ___ must change.

Answer: angle, length


Review Questions

The ___ slides on the transmission output shaft whenever the rear assembly moves.

Answer: slip yoke


Review Questions

True or False? A slip yoke has external splines.

Answer: False. A slip yoke has internal splines.


Review Questions

A swivel connection, or coupling, that allows the drive shaft assembly to transmit power smoothly is called a(n) ___.

Answer: universal joint


Review Questions

From the slip yoke, power flows into the ___ and then into the drive shaft.

Answer: front universal joint


Review Questions

A double Cardan U-joint is composed of two cross-and-roller U-joints connected by a(n) ___.

Answer: center yoke


Review Questions

A cross-and-roller U-joint is sometimes called a ___.

A. Cardan U-joint

B. conventional U-joint

C. double Cardan U-joint

D. Both A and B.

Answer: D. Both A and B.


Review Questions

True or False? The Hotchkiss drive is the most common type of drive shaft assembly.

Answer: True


Review Questions

In a two-piece drive shaft, the ___ keeps the drive shafts aligned.

Answer: center support bearing


Review Questions

Driveshaft assembly angles are measured at the front and rear ___.

Answer: U-joints

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Chapter 1