Chapter 8 Four-Wheel Drive Systems
Answers to Review Questions
•Classroom Manual, Pages 203–205
Short Answer Essays
1.The main advantage of a four-wheel drive vehicle over a two-wheel drive vehicle is improved traction and handling.
2.The main differences between four-wheel drive and all-wheel drive is that four-wheel drive uses a separate transfer case and allows the driver to select the transferring of the engine’s power to two or four wheels. All-wheel drives do not use a transfer case; instead, they use a center differential to transmit engine power to the front and rear axles. This system will not allow the driver to select between two- and four-wheel drive.
3.The transfer case receives the engine’s power from the transmission and transfers it to the drive shafts leading to the front and rear drive axles.
4.When the front locking hubs are locked to the front axles, four-wheel drive results; when they are unlocked, the front wheels are free to rotate at different speeds.
5.The differences between an integrated 4WD system and an “on-demand” 4WD system is that the integrated system uses either a computer or a clutch to adjust the torque split to the drive axles depending on which wheels have traction, while the on-demand system provides power to the second axle only when 4WD is selected by the driver.
6.A part-time 4WD system can be shifted from 2WD to 4WD. A full-time 4WD system is always in 4WD.
7.The three main components that are added to a 2WD system to make it 4WD are a transfer case, front drive shaft, and a front differential.
8.The purpose of an interaxle is to allow the rear and front wheels to turn at different speeds.
9.Chain drives are used in many transfer cases because they reduce weight, are efficient and quiet, and allow for drive gear placement flexibility.
10.A planetary gear set is made up of three major components: the sun gear, which is usually splined to the input shaft; the planetary gear assembly, which is comprised of the planet gears and carrier and is attached to the output shaft; and the ring gear. By holding or releasing the ring gear, gear reduction can be achieved through the sun gear driving the planetary gears and carrier.
Fill-in-the-Blanks
1.Four, two; four, four
2.Sun, pinion, planetary carrier, ring
3.Ring
4.Driveline wind-up
5.Independent front
6.Vacuum, electric, linkage
7.Two-wheel drive high, four-wheel drive high, neutral, four-wheel drive low
8.Locking
9.Locking hubs
10.Differential, drive shafts
Multiple Choice
1.C
2.C
3.B
4.C
5.A
6.C
7.C
8.D
9.A
10.D
•Shop Manual, Pages 353–354
ASE-Style Review Questions
1.B
2.C
3.B
4.C
5.A
6.A
7.C
8.C
9.B
10.B
ASE Challenge
1.B
2.C
3.A
4.C
5.D