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 Transmission rear seal
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 shaft or 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 joint or 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 cardan universal 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-trunnion joint seldom used

22. 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 Torque tube 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