Automotive Drive Axles

Constant Velocity (CV) Types

Drive Axle Components (fwd)

Drive Axle Components (rwd)

Outer CV-joint Allows wheels to steer while axle is rotating

Inner CV-joint Allows for suspension changes while axle is rotating

Axle shaft Transmits power from inner to outer CV-joint

ABS Speed Sensor

Some axle shafts have an

exciter ring

welded to the outboard CV joint for ABS operation. During removal and service of this style of axle

extreme care

must be used not to damage or move this ring.

Drive Axle Components

 Outer CV-joint  Allows wheels to steer while axle is rotating  Inner CV-joint  Allows for suspension changes while axle is rotating  Axle shaft  Transmits power from inner to outer CV-joint

Front Wheel Drive Issues

With the engine mounted transversely, the transaxle sits to one side of the engine compartment. Thus, one axle must be longer than the other.

Front Wheel Drive Issues

Front Wheel Drive Issues

Torque Steer - occurs when the

CV joints

on one drive shaft operate at different angles from those on the other shaft.

The joints on the longer shaft almost always operate at less of an angle

than those on the shorter shaft. With an

open

differential the shaft with the least resistance will receive more torque.

What?

1. A longer shaft will flex more thus being more forgiving at its outer angles.

2. A longer

shaft

will operate at more of an angle thus reducing the angles of the

joint

.

Front Wheel Drive Issues

When the differential sends power to the wheels, the longer shaft will have less resistance because the CV joints are operating at less of an angle. Most of the engines power will be sent to that side. This phenomenon results in what is called

torque steer

.

Torque Steer Remedies

Add an intermediate shaft

Torque Steer Remedies

Vibration dampers - Sometimes used to stabilize the shaft as it spins.

Torque Steer Remedies

Unequal length half-shafts - Usually constructed differently to reduce torque steer.

Types of Drive Axles

 Equal length shafts  Used to reduce torque steer  Vibration dampers  Sometimes used to dampen vibrations in the driveline  Unequal length half shafts  Usually constructed differently to prevent torque steer

Front wheel drive shafts turn at approximately 1/3 the speed of rear wheel drive shafts.

Why?

Benefits?

CV-Joint Types



Outboard joint

 Does not move in and out to change shaft length 

Fixed joint



Inboard joint

 Changes in length to allow movement of the suspension 

Plunging joint

Outboard Joint Movement

CV-Joint Types

Inboard Joint Movement

CV-Joint Types

CV-Joint Types

 Ball-type CV-joint  Was named after its designer, A.H. Rzeppa  Uses three to six steel balls held together by a steel cage  The balls ride in a socket to allow rotation and turning  Is used in most front-wheel-drive vehicles

Rzeppa Joint Exploded View

Rzeppa Joint - Exploded View

CV-Joint Types

Outboard Joints

(cont’d)

 Tripod-type joint  Uses a central hub (tripod) with three trunnions  Has roller bearings that ride on the trunnions  The outer surface of bearings ride in the joint or “tulip” housing  Allows for greater angles

Tripod Joint

Outboard Joint Movement

Inboard Plunging Tripod

Inboard Plunging Tripod

Inboard CV Joints

Ball-type (Double-offset) Joint Is similar to a Rzeppa joint but has elongated grooves in the inner race

Inboard CV Joints

Tripod-type joint Has longer grooves than a fixed-type joint to allow for plunging.

Inboard CV Joints

Cross Groove CV Joint •The grooves in the outer race are cut at an angle to allow for better movement.

CV-Joint Types

Inboard Joint Movement

CV-Joint Types

 Outboard joint types  Rzeppa fixed tripod  Inboard joint types  Double-offset  Plunging tripod  Cross-groove plunge joint

CV-Joint

 All CJ joints have a rubber, plastic or neoprene boot to protect the internal parts.

 The boots are fastened by clamps at either end.

 All CV joints must be lubricated. 

CV joint grease

differs from standard wheel bearing or chassis grease. They cannot be interchanged!

CV-Joint

 Constant velocity joints are called as such because they are designed to transfer a uniform torque and a constant speed through a wide variety of angles.

FWD Wheel Bearing Styles

 Double-row, angular contact bearings  Are used on most General Motors, DaimlerChrysler, and European cars  Have two rows of ball bearings located next to each other  Opposed tapered-roller bearings  Are used on Fords and most Asian cars

FWD Wheel Bearing Styles

 The axle nut not only secures the end of the axle but it also sets the wheel bearing pre-load.

Diagnosing CJ Joints & Axles

Bad CV joints will generally make a clunking or clicking noise. Outer joints will make noise on turns.

Diagnosing CJ Joints & Axles

Bad CV joints will generally make a clunking or clicking noise. Inner joints will make noise over bumps.

Perform a Road Test

 Drive the car under various conditions such as accelerating, coasting, turning, and weaving side to side  Listen for clicking or clunking, especially while turning  Feel for shudder, shimmy, vibration, or any other abnormalities

Diagnosing CJ Joints & Axles

 Do not confuse CV joint noises with outer wheel bearing noises. 

CV joint

noises will be more noticeable at slower speeds.



Wheel bearing

noises will have a higher pitch grind or whine. They will also be more noticeable at higher speeds on turns.

Visual Inspection

 Check out all other problem areas before assuming that the problem is being caused by the axle assembly  Check the CV-boots for tears and grease leaks  Check the shafts for damage or being bent  Move the shaft, wheels, and other components to check for looseness

Visual Inspection

Possible Reasons for CV Boot Failure

 Cuts or tears from foreign objects  Accident damage  Improper towing hook-up or service techniques  Ice forming around boot  Deterioration  Clamp failure

Off-Car Axle Inspection

    Be careful not to overtighten the shaft in the vise Look for cracks, chips, pits, or rust on all components Check the joint for sticking while plunging it in and out Check for discoloring usually caused by heat

Boot Replacement Tips

    Mark the location of the joint to the shaft Inspect the grease for contamination Make sure the new boot clamps are secure Use a dull screwdriver to remove trapped air from the boot

CV-Joint Replacement Tips

 Clean the joint thoroughly so a complete inspection can be made  Refer to the service manual to find out how the joint is retained to the shaft  Pack the new joint using all of the lubricant supplied

FWD Wheel Bearing Inspection

 Excessive play inspection  Usually checked by pulling outward at the top of the tire and pushing inward at the bottom with the vehicle supported under the control arm  Noise inspection  Bearing noise will often increase when the vehicle is turned

Front Wheel Drive Service

 Anytime a front axle or wheel bearing is serviced the axle retaining nut MUST be torqued to manufacturer specifications.

Rear Wheel Drive Axle Shafts

Drive Shaft Purposes

 Transmits power from the transmission to the differential  Allows the transmission and the rear axle assembly to be at different heights  Allows the rear axle to move up and down while maintaining a connection to the transmission

Drive Shaft Features

 Can be made of steel, aluminum, or composite material  May have cardboard liner to reduce noise  Has a yoke welded to each end  Universal joints are used to connect to pinion flange yoke and sleeve yoke  May have balance weights attached

Drive Shaft Designs

 Hotchkiss design  Can be one piece or two piece  The shaft and joints are external  Two piece Design  Uses a carrier (center) bearing to stabilize the center of the driveshaft

Drive Shaft Designs Torque tube: uses rigid tube with no universal joints Flexible type: A flexible steel rope; rarely used today

Universal Joints

 Are sometimes referred to as Cardan, Spicer, cross, four-point, or Hooke joints  Allow for angle changes between the drive shaft, the transmission output shaft, and the rear axle housing

Universal Joint Characteristics

 Speed variations  While operating at an angle, U-joints speed up and slow down twice per revolution  Joint phasing  The vibrations caused by one U-joint are transmitted to the other one

Universal Joint Characteristics

Universal Joint Phasing

Universal Joint Characteristics

(cont’d)

 Canceling angles  The angle of the front U-joint is offset by the rear one  The correct angle must be maintained to minimize vibration

Universal Joint Designs

 Single universal joint  Sometimes known as single Cardan/Spicer Universal joint  Consists of a cross and four needle bearings  Double Cardan joint  Consists of two single U-joints joined by a center yoke and a ball and socket

Universal Joint Designs

Universal Joint Designs

Universal Joints

 Double Cardan Type: Sometimes referred to as a Constant Velocity universal joint.  Used on Luxury RWD cars  … and PU trucks

Universal Joint Designs

(cont’d)

 Slip Yolk  Allows for changes in driveshaft length caused by suspension travel  Components include:  Transmission output shaft  The slip joint  A yoke and U-joint  The driveshaft

Type A Clips

Type B Clips

Methods of Mounting Universal Joints

 Bearing plate  Cap and bolt  Thrust plate  U-bolt  Wing bearing  Strap

Universal Joint Maintenance

 Most factory-installed universal joints are sealed and don’t require periodic lubrication  After-market replacement joints are equipped with a grease fitting and must be greased periodically

Drive Shaft Problem Diagnosis

 Road testing  Vehicle should be driven while accelerating and decelerating as well as at various steady speeds  Vibrations caused by worn U-joints usually occur while accelerating

Types and Causes of Vibrations

 High speed vibrations  Usually caused by driveshaft imbalance  Vibrations during acceleration  Usually caused by worn double Cardan joint ball and socket  Low speed vibrations  Usually caused by improper operating angles

Noise Diagnosis

 Clunking noise while accelerating from a dead stop  Usually caused by worn or damaged U-joint  Can be caused by problems including excessive clearance between slip joint and extension housing  Squeaking noise  Often caused by worn or poorly lubricated U-joint

Reasons for Universal Joint Failure

 Lack of lubrication  Pushing another car  Towing a trailer  Changing gears abruptly  Carrying heavy loads  Beating the heck out of your car

Inspecting the Drive Shaft

 Check for fluid leaks  Check the U-joints for signs of rust or leakage  Check for movement in the joint while trying to turn the yoke and the shaft in opposite directions  Check the drive shaft for dents, missing weights, and undercoating or dirt  Check for binding U-joints

Tips for Removing and Installing a Drive Shaft

 Always mark the pinion flange and the end yoke before disassembly  Use a plug on the transmission extension housing to prevent fluid loss  Line up all index marks  Torque bolts to manufacturer’s specifications

Tips for Disassembling a U-Joint

 Index the joint’s components before disassembly  Remove all retaining rings before pressing on the spider  Use a U-joint tool kit, socket and vise, c-clamp, or press to press the spider from the yoke

Tips for Disassembling a U-Joint

 Most General Motors Universal Joints are kept in place with organic or fiberglass retainers  The caps must be heated with a torch to “pop” the retainers free

Tips for Assembling a U Joint

 Clean all components before assembly  Turn the spider while tightening to ensure the trunions move freely on the bearings  Take care not to tear the bearing seal during assembly  Fill new joint with grease (if equipped with a fitting)

Causes of Drive Shaft Imbalance

 Damage from rocks and debris  Balance weights fallen off  Dirt or mud stuck on drive shaft  Undercoating sprayed on drive shaft

Measuring Operating Angle

     Make sure the vehicle is empty and the gas tank is full Use inclinometer to measure U-joint angles Follow the service manual procedures Compare front and rear angles The difference between the two angles is the operating angle

Measuring Operating Angle The difference between the two angles is the operating angle

Causes of Drive Shaft Imbalance

 Damage from rocks and debris  Balance weights fallen off  Dirt or mud stuck on drive shaft  Undercoating sprayed on drive shaft  Improper service

Steps for Checking Imbalance

1. Set up vehicle to be run on a lift 2. While vehicle is running, use chalk to mark the high spot on the shaft 3. Stop vehicle and install two large hose clamps to the shaft with the screw assembly opposite the chalk mark 4. Run engine to the desired speed again

Steps for Checking Imbalance

(cont’d)

5. If the vibration is gone, road test the vehicle 6. If the vibration is still felt, rotate the clamps away from each other in equal amounts and repeat test 7. Repeat the procedure until no vibration is felt

Measuring Drive Shaft Runout

 Use a dial indicator  Measure at the center and at both ends of shaft  Refer to manufacturer’s specifications for acceptable runout  Replace the shaft if runout is greater than allowed

Summary

 The purpose of the drive shaft is to transmit power from the transmission to the rear end while allowing for changes in suspension height  Universal joints allow for angle changes between the drive shaft, the transmission output shaft, and the rear axle housing  Hotchkiss-type drive shafts are commonly used today  Universal joints can be single or double Cardan joints

Summary

(cont’d)

 Universal joints and drive shafts require little maintenance  Diagnosing drive shaft concerns usually involves a road test and a visual inspection  Servicing drive shaft components requires following specific service procedures  Several checks can be performed, including balance, runout, and operating angle