Automotive Drive Axles

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Automotive Drive Axles

• Constant Velocity (CV) Types

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Drive Axle Components (fwd)
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Drive Axle Components (rwd)
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Outer CV-joint Allows wheels to steer while
axle is rotating
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Inner CV-jointAllows for suspension changes
while axle is rotating
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Axle shaftTransmits power from inner to outer
CV-joint
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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.
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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

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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.
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Front Wheel Drive Issues
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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.
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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.
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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.
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Torque Steer Remedies
Add an intermediate shaft
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Torque Steer Remedies
Vibration dampers - Sometimes used to stabilize
the shaft as it spins.
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Torque Steer Remedies
Unequal length half-shafts - Usually constructed
differently to reduce torque steer.
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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

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

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Outboard Joint Movement
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CV-Joint Types
Inboard Joint Movement
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CV-Joint Types
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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

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Rzeppa Joint - Exploded View
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Rzeppa Joint - Exploded View
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CV-Joint Types
Outboard Joints (contd)

• 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

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Tripod Joint
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Outboard Joint Movement
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Inboard Plunging Tripod
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Inboard Plunging Tripod
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Inboard CV Joints
Ball-type (Double-offset) Joint Is similar to a
Rzeppa joint but has elongated grooves in the
inner race
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Inboard CV Joints
Tripod-type joint Has longer grooves than a
fixed-type joint to allow for plunging.
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Inboard CV Joints

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

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CV-Joint Types
Inboard Joint Movement
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CV-Joint Types

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

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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!

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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.

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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

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FWD Wheel Bearing Styles

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

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Diagnosing CJ Joints Axles
Bad CV joints will generally make a clunking or
clicking noise. Outer joints will make noise on
turns.
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Diagnosing CJ Joints Axles
Bad CV joints will generally make a clunking or
clicking noise. Inner joints will make noise over
bumps.
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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

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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.

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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

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Visual Inspection
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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

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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

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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

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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

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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

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Front Wheel Drive Service

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

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Rear Wheel Drive Axle Shafts
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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

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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

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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

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

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Universal JointCharacteristics

• 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

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Universal JointCharacteristics
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Universal JointPhasing
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Universal Joint Characteristics (contd)

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

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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

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Universal Joint Designs
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Universal Joint Designs
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Universal Joints

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

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Universal Joint Designs (contd)

• 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

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Type A Clips
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Type B Clips
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Methods of MountingUniversal Joints

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

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Universal Joint Maintenance

• Most factory-installed universal joints are
  sealed and dont require periodic lubrication
• After-market replacement joints are equipped with
  a grease fitting and must be greased periodically

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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

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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

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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

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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

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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

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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 manufacturers specifications

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Tips for Disassembling a U-Joint

• Index the joints 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

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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

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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)

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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

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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

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

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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

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Steps for Checking Imbalance (contd)

• 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

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Measuring Drive Shaft Runout

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

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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

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Summary (contd)

• 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