1. Modern Automotive Technology PowerPoint for by Russell Krick
Publisher The Goodheart-Willcox Co., Inc. Tinley Park, Illinois

2. Chapter 59
Drive Shafts and
Transfer Cases

3. Contents
Drive shaft assembly
Drivelines
Transfer cases

4. Connects the transmission output shaft with the rear axle assembly
Drive Shaft Assembly
Connects the transmission output shaft with the rear axle assembly

5. Components Slip yoke Front universal joint Drive shaft
Rear universal joint
Rear yoke

6. Functions
Sends turning power from the transmission to the rear axle assembly
Flexes and allows vertical movement of the rear axle assembly
Provides a sliding action to adjust for changes in driveline length
Provides smooth power transfer

7. Operation The transmission output shaft turns the slip yoke
The slip yoke turns the front universal joint, driveshaft, rear universal joint, and rear yoke on the differential

8. Driveline Flex
Universal joints let the driveline flex as the rear axle moves up and down

9. Slip Yoke Splined to the transmission output shaft
Allows for changes in driveline length by sliding in and out of the transmission
The outer diameter is machined smooth, providing a bearing surface for the bushing and oil seal in the transmission

10. Slip Yoke

11. Drive Shaft Hollow steel tube with permanent yokes welded on each end
Very strong and light
Lightweight units may be made of thin-wall aluminum with longitudinally aligned graphite fibers for added strength
May be single-piece, or two-piece

12. Typical drive shaft assembly

13. Drive Shaft Balance
In high gears, the drive shaft turns at the same speed as the engine
The shaft must be accurately balanced
The shaft is rotated on a balancing machine at the factory
Steel balancing weights are welded to the shaft to reduce vibration

14. Drive Shaft Balancing Weights

15. Vibration Damper
The drive shaft may be equipped with a large, ring-shaped weight mounted on rubber
Helps keep the shaft turning smoothly by absorbing torsional vibration

16. Universal Joint
Swivel connection capable of transferring a turning force between shafts at an angle to one another
Made of two Y-shaped yokes, connected by a cross
Bearings on each end of the cross allow the yokes to swing into various angles while turning

17. Universal Joint

18. Types of Universal Joints

19. Cross-and-Roller

20. Cross-and-Roller Cardan universal joint Most common type of joint
The bearing caps are held stationary in the drive shaft yoke
The roller bearings reduce friction
The cross is free to rotate inside the caps and yokes

21. Several methods are used to retain the bearing cap in the yoke
Bearing Cap Retention
Several methods are used to retain the bearing cap in the yoke

22. Cross-and-Roller Drive Shaft Assembly

23. Constant Velocity Joint
A cross-and-roller joint tends to accelerate and decelerate during each revolution, setting up torsional vibrations
A constant velocity joint has two cross-and-roller joints connected by a centering socket and center yoke
By using two joints, the output shaft speed fluctuations are counteracted

24. Constant Velocity Joint
Speed changes at the output of the first joint are offset by speed changes at the other joint

25. Constant Velocity Drive Shaft

26. Ball-and-Trunnion Joint
Constant velocity design
Eliminates shaft speed fluctuations
Allows for slight length changes in the driveline

27. Center Support Bearing
Holds the middle of a two-piece drive shaft
Bolts to the vehicle’s frame or body
Common on pickup trucks and large vehicles with long wheel bases
The rubber mount prevents noise and vibration from transferring into the passenger compartment

28. Center Support Bearing

29. Center Support Bearing

30. Two main types—Hotchkiss driveline and torque tube driveline
Drivelines
Two main types—Hotchkiss driveline and torque tube driveline

31. Hotchkiss Driveline
An exposed drive shaft operates a rear axle assembly mounted on springs
Most common type of driveline
Universal joints are used at both ends of the drive shaft
Cross-and-roller universal joints are most commonly used

32. Torque Tube Driveline
Uses a solid steel drive shaft enclosed in a large hollow tube
Only one swivel joint is used at the front
The rear of the torque tube is a rigid part of the rear axle housing

33. Transfer Cases
Used to send power to both the front and rear axle assemblies in a four-wheel-drive vehicle
Mounted behind, and driven by, the transmission
Two drive shafts run from the transfer case, one to each drive axle

34. Transfer Case

35. Four-Wheel Drive versus All-Wheel Drive
Four-wheel drive has a transfer case separate from the transmission
drive ranges such as 2H, 4H, and 4L are provided
All-wheel drive has the transfer case included as part of the transaxle

36. Four-Wheel Drive versus All-Wheel Drive

37. Transfer Case Construction
Constructed much like a manual transmission
uses shift forks, splines, gears, shims, and bearings
Made of cast iron or aluminum
Filled with lubricant (oil) that cuts friction

38. Transfer Case Construction

39. Transfer Case Ranges Two-wheel drive, high range (2H)
normally provides a gear ratio of 1:1
Four-wheel drive, high range (4H)
Four-wheel drive, low range (4L)
normally provides a gear ratio of approximately 2:1

40. Power Flow

41. Two-Wheel Drive (High Range)
Provided for normal driving when four-wheel drive is not needed
Torque flows from the input gear to the locked planet gears and ring gear, which rotate as a single unit
Torque is transferred to the main shaft through the planet carrier
Power flows out the rear yoke

42. Four-Wheel Drive (High Range)
Torque flows through the input gear, the planet gears, and ring gear as in 2H
The sliding clutch is shifted into the main clutch gear
Torque flows through the drive chain, to the front output yoke, to drive the front axle assembly
Both axles drive the vehicle

43. Four-Wheel Drive (Low Range)
Torque transfer is almost the same as in 4H
The ring gear is shifted forward into the lock plate, holding the ring gear stationary
The planet gears walk inside the ring gear, producing a gear reduction

44. All-Wheel Drive Does not use a conventional transfer case
Designed for a front-wheel-drive transaxle or a transmission
The transmission or transaxle is modified to allow power flow to the front and rear drive axles

45. All-Wheel Drive
A fluid coupling controls the power split to the front and rear axle assemblies