Drive Shaft and Transfer Case Technology

2. 68 Chapter Drive Shaft and Transfer Case Technology

3. Objectives After studying this chapter, you will be able to: • Identify and describe the parts of a modern drive shaft assembly. • Explain the functions of a drive shaft. • Describe the different types of universal joints. • List the different types of drivelines. • Explain the basic operation of a transfer case. • Correctly answer ASE certification test questions that require a knowledge of drive shafts and transfer cases.

4. Drive Shaft Assembly Drive shaft assembly components • Slip yoke • Connects transmission output shaft to front universal joint • Drive shaft • Hollow metal tube that transfers turning power from front universal joint to rear universal joint

5. Drive Shaft Assembly (Cont.) • Rear universal joint • Flex joint connecting drive shaft to rear yoke • Rear yoke • Holds rear universal joint and transfers torque to gears in rear axle assembly and differential

6. Drive Shaft Assembly (Cont.) (Mazda)

7. Functions of Drive Shaft Assembly • Sends turning power from transmission to rear axle assembly • Flexes and allows vertical movement of rear axle assembly • Provides sliding action to adjust for changes in driveline length • Provides smooth power transfer

8. Drive Shaft Operation • Transmission output shaft turns slip yoke • Slip yoke then turns front universal joint, drive shaft, rear universal joint, and rear yoke on differential • Differential contains gears that transfer power to rear drive axles • Axles rotate wheels

9. Driveline Flex • When tires strike a bump in the road, rear suspension moves upward and springs are compressed • Universal joints • Let driveline flex as rear axle moves up and down • Protects drive shaft from any damage caused by movement

10. Slip Yoke • Slip yoke, or slip joint • Splined to transmission output shaft • Allows for changes in driveline length by sliding in and out of transmission (Ford)

11. Slip Yoke (Cont.) • Extension housing bushing • Supports slip yoke as it spins in transmission • Transmission rear seal • Rides on slip yoke and prevents fluid leakage from rear of transmission

12. Rear Yoke • Rear yoke is yoke bolted to outer end of pinion gear on rear axle assembly • It transfers torque to gears in rear axle assembly • Rear universal joint held by this yoke

13. Drive Shaft • Drive shaftor propeller shaft • Hollow steel tube with permanent yokes welded on each end • Very strong and light • Spins much faster than wheels and tires • It must be straight and perfectly balanced

14. Drive Shaft Assembly (Toyota)

15. Drive Shaft Balance • Drive shaft must be perfectly balanced, with its weight evenly distributed around its centerline • Drive shaft balancing weights • Welded to shaft to reduce vibration • Drive shaft vibration damper • Large, ring shaped weight mounted on rubber • Helps keep shaft spinning smoothly by absorbing torsional vibration

16. Universal Joints • Universal jointor U-joint • Swivel connection capable of transferring turning force between shafts at angle to one another • Simple universal joint made of two Y-shaped yokes (knuckles) connected by cross (spider)

17. Cross-and-Roller Universal Joint • Cross-and-roller joint or cardanuniversal joint • Most common type of drive shaft universal joint • Bearing caps are held stationary in drive shaft yokes • Roller bearings fit between caps and cross to reduce friction • Cross is free to rotate inside caps and yokes

18. Cross-and-Roller Universal Joint(Cont.) (Chrysler)

19. Constant Velocity Universal Joint • Constant velocity universal joint or double-cardan joint • Two cross-and-roller joints connected by centering socket and center yoke • Two joints operate together on one end of drive shaft • Output shaft speed fluctuations are counteracted

20. Constant Velocity Universal Joint(Cont.) (Ford)

21. Ball-and-Trunnion Universal Joint • Ball-and-trunnion joint • Another joint designed for constant velocity • Eliminates shaft speed fluctuations • Allows for slight length changes in driveline • Ball-and-trunnionjoint seldom used

22. Center Support Bearing • Center support bearing • Holds middle of two-piece drive shaft • Center bearing bolts to vehicle’s frame or underbody • Supports center of drive shaft where two shafts come together

23. Center Support Bearing(Cont.) (Fiat)

24. Driveline Types • Hotchkiss driveline • Exposed drive shaft that operates rear axle assembly mounted on springs • Usually has cross-and-roller universal joints • Torque tube driveline • Solid steel drive shaft enclosed in large hollow tube • With independent rear suspension, drive shaft can be one piece without universal joint

25. Hotchkiss Driveline (Ford)

26. Transfer Cases • Transfer case • Sends power to both front and rear axle assemblies in four-wheel-drive vehicle • Mounts behind and is driven by transmission • Two drive shafts normally run from transfer case, one to each drive axle

27. Transfer Cases (Cont.) (Ford)

28. Two-Wheel-Drive, High Range (2H) • 2H range provided for normal driving when four-wheel-drive traction not needed • Sliding clutch remains in neutral position • Torque is not transferred to front axle assembly

29. Four-Wheel-Drive, High Range (4H) • Sliding clutch is shifted into main shaft clutch gear • Torque then flows through drive chain, front output yoke, and front drive axle assembly • Both front and rear axles drive vehicle

30. Four-Wheel-Drive, Low Range (4L) • Torque transfer is almost same as in 4H • Ring gear is shifted forward into lock plate • This holds ring gear stationary • Planet gears walk inside ring gear, producing gear reduction

31. All-Wheel Drive • All-wheel drive • Four-wheel-drive system that does not use conventional transfer case • Designed for front-wheel-drive transaxle or transmission • Transmission or transaxle in all-wheel-drive system is modified to allow power flow to front and rear drive axles

32. Drive Systems