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Chapter 20

Chapter 20. Front-Wheel Drive CV Joint Fundamentals and Service. Introduction. Front-wheel drive vehicles have a transaxle that combines both transmission and differential in one unit. Drive axles with constant velocity (CV) joints extend from the ends of the transaxle.

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Chapter 20

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  1. Chapter 20 Front-Wheel Drive CV Joint Fundamentals and Service

  2. Introduction • Front-wheel drive vehicles have a transaxle that combines both transmission and differential in one unit. • Drive axles with constant velocity (CV) joints extend from the ends of the transaxle.

  3. Front-Wheel Drive Axles • Front-wheel drive axles are equipped with CV joints. • CV joints are necessary because universal joints cannot operate at the angles needed. • CV joints allow the drive axle to change length and turn.

  4. Front-Wheel Drive Axles(continued) • Front-wheel drive axles operate more slowly than a rear-wheel drive shaft because the front wheel axles have already been through the gear reduction of the differential.

  5. Axle Shaft Parts • Drive axles are also called half shafts, or axle shafts. • There is a short shaft splined into the front wheel bearing called a stub shaft.

  6. Axle Shaft Parts(continued) • The transmission end of the shaft may have another stub shaft, or a female end that fits over a male transmission output shaft.

  7. CV Joints • There are three ways to classify a CV joint: • Inboard and outboard. • Fixed and plunge. • Ball and tripod.

  8. CV Joints(continued) • The inside end of the drive axle is called the inboard joint. • The outside end of the drive axle is called the outboard joint.

  9. Plunge CV Joints • The inboard joint is the plunge joint. • The plunge joint has the capability to change its length with the movement of the suspension. • The plunge joint also transmits movement.

  10. Fixed Joints • The outboard joint is also called the fixed joint. • The fixed joint is responsible for pivoting as the steering is turned.

  11. CV Joint Construction The most common types of CV joints: • The Rzeppa joint for the outer or fixed joint. • The tripod joint for the plunging, or inboard joint.

  12. Axle Shaft Design • Early designs used two unequal-length drive shafts. • This caused torque steer in some higher-performance models. • The longer shaft tended to twist more than the short shaft, and torque delivery was unequal.

  13. Axle Shaft Design(continued) • One way to prevent torque steer was to make the longer shaft out of larger diameter tubing, or use an extension (intermediate) shaft on the transmission. • Currently, manufacturers try to keep axle lengths as close to equal as possible.

  14. CV Boot Service • Most CV joint boots are designed to last about 75,000 miles. • If the boot is leaking, the CV joint will fail from lack of grease in a short amount of time.

  15. Axle Inspection and Diagnosis • Check for obvious looseness. • Check for leaking boots. • Clicking sounds that change with speed during turns could be caused by a bad outboard joint.

  16. Axle Inspection and Diagnosis(continued) • A bad plunge or inboard joint can cause a clunking sound when starting from a stop, or during deceleration and/or braking. • The axle may have to be disassembled to find the cause of a problem.

  17. Axle Shaft Repair • If the axle joint is damaged, the technician will have to decide whether to repair or replace the axle. • Be sure to follow manufacturer’s guidelines for removing, replacing, and rebuilding axles.

  18. Axle Shaft Repair (continued) • Often, the most economical repair is replacement of the entire axle with a rebuilt axle. • The rebuilt axle can cost less than a single joint.

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