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 zOuter CV-joint yAllows wheels to steer while axle is rotating zInner CV-joint yAllows for suspension changes while axle is rotating zAxle shaft yTransmits 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.
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. Front Wheel Drive Issues
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.
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. Front Wheel Drive Issues
Torque Steer Remedies Add an intermediate shaft
Torque Steer Remedies Vibration dampers - Sometimes used to stabilize the shaft as it spins.
Unequal length half-shafts - Usually constructed differently to reduce torque steer. Torque Steer Remedies
Types of Drive Axles zEqual length shafts yUsed to reduce torque steer zVibration dampers ySometimes used to dampen vibrations in the driveline zUnequal length half- shafts yUsually 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 zOutboard joint yDoes not move in and out to change shaft length yFixed joint zInboard joint yChanges in length to allow movement of the suspension yPlunging joint
zBall-type CV-joint yWas named after its designer, A.H. Rzeppa yUses three to six steel balls held together by a steel cage yThe balls ride in a socket to allow rotation and turning yIs used in most front-wheel-drive vehicles
CV-Joint Types Outboard Joints (cont’d) zTripod-type joint yUses a central hub (tripod) with three trunnions yHas roller bearings that ride on the trunnions yThe outer surface of bearings ride in the joint or “tulip” housing yAllows for greater angles
CV-Joint zAll CJ joints have a rubber, plastic or neoprene boot to protect the internal parts. zThe boots are fastened by clamps at either end. zAll CV joints must be lubricated. zCV joint grease differs from standard wheel bearing or chassis grease. They cannot be interchanged!
CV-Joint zConstant 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 zDouble-row, angular- contact bearings yAre used on most General Motors, DaimlerChrysler, and European cars yHave two rows of ball bearings located next to each other zOpposed tapered-roller bearings yAre used on Fords and most Asian cars
zThe axle nut not only secures the end of the axle but it also sets the wheel bearing pre-load. FWD Wheel Bearing Styles
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 zDrive the car under various conditions such as accelerating, coasting, turning, and weaving side to side zListen for clicking or clunking, especially while turning zFeel for shudder, shimmy, vibration, or any other abnormalities
zDo not confuse CV joint noises with outer wheel bearing noises. zCV joint noises will be more noticeable at slower speeds. zWheel bearing noises will have a higher pitch grind or whine. They will also be more noticeable at higher speeds on turns. Diagnosing CJ Joints & Axles
Visual Inspection zCheck out all other problem areas before assuming that the problem is being caused by the axle assembly zCheck the CV-boots for tears and grease leaks zCheck the shafts for damage or being bent zMove the shaft, wheels, and other components to check for looseness
Possible Reasons for CV- Boot Failure zCuts or tears from foreign objects zAccident damage zImproper towing hook-up or service techniques zIce forming around boot zDeterioration zClamp failure
Off-Car Axle Inspection zBe careful not to overtighten the shaft in the vise zLook for cracks, chips, pits, or rust on all components zCheck the joint for sticking while plunging it in and out zCheck for discoloring usually caused by heat
Boot Replacement Tips zMark the location of the joint to the shaft zInspect the grease for contamination zMake sure the new boot clamps are secure zUse a dull screwdriver to remove trapped air from the boot
CV-Joint Replacement Tips zClean the joint thoroughly so a complete inspection can be made zRefer to the service manual to find out how the joint is retained to the shaft zPack the new joint using all of the lubricant supplied
FWD Wheel Bearing Inspection zExcessive play inspection yUsually checked by pulling outward at the top of the tire and pushing inward at the bottom with the vehicle supported under the control arm zNoise inspection yBearing noise will often increase when the vehicle is turned
Front Wheel Drive Service zAnytime a front axle or wheel bearing is serviced the axle retaining nut MUST be torqued to manufacturer specifications.
Drive Shaft Purposes zTransmits power from the transmission to the differential zAllows the transmission and the rear axle assembly to be at different heights zAllows the rear axle to move up and down while maintaining a connection to the transmission
Drive Shaft Features zCan be made of steel, aluminum, or composite material zMay have cardboard liner to reduce noise zHas a yoke welded to each end zUniversal joints are used to connect to pinion flange yoke and sleeve yoke zMay have balance weights attached
Drive Shaft Designs zHotchkiss design yCan be one piece or two piece yThe shaft and joints are external zTwo piece Design yUses 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 zAre sometimes referred to as Cardan, Spicer, cross, four-point, or Hooke joints zAllow for angle changes between the drive shaft, the transmission output shaft, and the rear axle housing
Universal Joint Characteristics zSpeed variations yWhile operating at an angle, U-joints speed up and slow down twice per revolution zJoint phasing yThe vibrations caused by one U-joint are transmitted to the other one
Universal Joint Characteristics (cont’d) zCanceling angles yThe angle of the front U-joint is offset by the rear one yThe correct angle must be maintained to minimize vibration
Universal Joint Designs zSingle universal joint ySometimes known as single Cardan/Spicer Universal joint yConsists of a cross and four needle bearings zDouble Cardan joint yConsists of two single U-joints joined by a center yoke and a ball and socket
Methods of Mounting Universal Joints zBearing plate zCap and bolt zThrust plate zU-bolt zWing bearing zStrap
Universal Joint Maintenance zMost factory-installed universal joints are sealed and don’t require periodic lubrication zAfter-market replacement joints are equipped with a grease fitting and must be greased periodically
Drive Shaft Problem Diagnosis zRoad testing yVehicle should be driven while accelerating and decelerating as well as at various steady speeds yVibrations caused by worn U-joints usually occur while accelerating
Types and Causes of Vibrations zHigh speed vibrations yUsually caused by driveshaft imbalance zVibrations during acceleration yUsually caused by worn double Cardan joint ball and socket zLow speed vibrations yUsually caused by improper operating angles
Noise Diagnosis zClunking noise while accelerating from a dead stop yUsually caused by worn or damaged U-joint yCan be caused by problems including excessive clearance between slip joint and extension housing zSqueaking noise yOften caused by worn or poorly lubricated U-joint
Reasons for Universal Joint Failure zLack of lubrication zPushing another car zTowing a trailer zChanging gears abruptly zCarrying heavy loads zBeating the heck out of your car
Inspecting the Drive Shaft zCheck for fluid leaks zCheck the U-joints for signs of rust or leakage zCheck for movement in the joint while trying to turn the yoke and the shaft in opposite directions zCheck the drive shaft for dents, missing weights, and undercoating or dirt zCheck for binding U-joints
Tips for Removing and Installing a Drive Shaft zAlways mark the pinion flange and the end yoke before disassembly zUse a plug on the transmission extension housing to prevent fluid loss zLine up all index marks zTorque bolts to manufacturer’s specifications
Tips for Disassembling a U-Joint zIndex the joint’s components before disassembly zRemove all retaining rings before pressing on the spider zUse a U-joint tool kit, socket and vise, c-clamp, or press to press the spider from the yoke
zMost General Motors Universal Joints are kept in place with organic or fiberglass retainers zThe caps must be heated with a torch to “pop” the retainers free Tips for Disassembling a U-Joint
Tips for Assembling a U- Joint zClean all components before assembly zTurn the spider while tightening to ensure the trunions move freely on the bearings zTake care not to tear the bearing seal during assembly zFill new joint with grease (if equipped with a fitting)
Causes of Drive Shaft Imbalance zDamage from rocks and debris zBalance weights fallen off zDirt or mud stuck on drive shaft zUndercoating sprayed on drive shaft
Measuring Operating Angle zMake sure the vehicle is empty and the gas tank is full zUse inclinometer to measure U-joint angles zFollow the service manual procedures zCompare front and rear angles zThe 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 zDamage from rocks and debris zBalance weights fallen off zDirt or mud stuck on drive shaft zUndercoating sprayed on drive shaft zImproper 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 zUse a dial indicator zMeasure at the center and at both ends of shaft zRefer to manufacturer’s specifications for acceptable runout zReplace the shaft if runout is greater than allowed
Summary zThe purpose of the drive shaft is to transmit power from the transmission to the rear end while allowing for changes in suspension height zUniversal joints allow for angle changes between the drive shaft, the transmission output shaft, and the rear axle housing zHotchkiss-type drive shafts are commonly used today zUniversal joints can be single or double Cardan joints
zUniversal joints and drive shafts require little maintenance zDiagnosing drive shaft concerns usually involves a road test and a visual inspection zServicing drive shaft components requires following specific service procedures zSeveral checks can be performed, including balance, runout, and operating angle Summary (cont’d)