Chapter 9 Answers to Review Questions



Chapter 9 Answers to Review Questions

CLASSROOM MANUAL, PAGES 308-310

SHORT ANSWER ESSAYS

1. Reaction members are those parts of a planetary gearset that are held in order to produce an output motion. Other members of the planetary gearset react against the stationary or held member.

2. Because of the location of the servo and band anchor, the band becomes self-energized and wraps itself around the drum in the same direction as drum rotation. This self-energizing effect reduces the force that the servo must produce to hold the band.

3. A multiple-disc pack also contains one or more return springs, return spring retainers, seals, one or more pressure plates, and snap rings. The seals hold in the hydraulic pressure during application of the pack. A pressure plate is a heavy metal plate that provides the clamping surface for the plates and is installed at one end or both ends of the pack. The snap rings are used to hold the parts in the pack together. In a typical pack, the apply piston at the rear of the drum is held in place by the return springs and a spring retainer secured by a snap ring. Hydraulic pressure moves the piston against return spring pressure and clamps the plates against the pressure plate. The friction between the plates locks them together, causing them to turn as a unit.

4. The multiple-friction disc pack can be used to drive or hold a member of the planetary gearset by connecting the member to the transmission’s case or to a clutch drum.

5. Two types of single-wrap bands are commonly used in transmissions today. One type is made of light and flexible steel and the other type is made of heavy and more rigid cast iron. The heavy bands are typically made with a metallic lining material that can withstand large gripping pressures. Light bands are lined with a less-abrasive material that helps limit drum wear.

6. A Belleville spring acts to improve the clamping force of the assembly, and as a piston return spring. The spring is locked into a groove inside the drum by a snap ring. As the piston moves to apply the pack, it moves the inner ends of the Belleville spring fingers into contact with the pressure plate to apply the assembly. The spring’s fingers act as levers against the pressure plate and increase the application force of the pack. When hydraulic pressure to the piston is stopped, the spring relaxes and returns to its original shape. The piston is forced back, and the pack is released.

7. Accumulators rely on the action of a piston or a valve to delay the delivery of high pressure to a clutch or band. An accumulator works like a shock absorber and cushions the application of servos and disc packs. An accumulator cushions sudden increases in hydraulic pressure by temporarily diverting some of the apply fluid into a parallel circuit or chamber. This allows the pressure to gradually increase and provides for smooth engagement of a brake or clutch.

8. “Shift Feel” is controlled by the pressure at which each reaction member is applied or released, the rate at which each is pressurized or exhausted, and the relative timing of the apply and release of the members. It is also affected by fluid type, the momentary engagement of a component in a different circuit, pulsed pressures, the clearance of the apply devices, and many more design features of the various transmission models.

9. A roller clutch utilizes roller bearings held in place by springs to separate the inner and outer races of the clutch assembly. Around the inside of the outer race are several cam-shaped indentations. The rollers and springs are located in these pockets. Rotation of one race in one direction locks the rollers between the two races, causing both to rotate together. When a race is rotated in the opposite direction, the roller bearings move into the pockets and are not locked between the races. A one-way sprag clutch consists of a hub and a drum separated by figure-eight-shaped metal pieces called sprags. The sprags are shaped in such a manner that they lock between the races when a race is turned in one direction only. Between the inner and outer races of the clutch are the sprags, cages, and springs. The sprags are longer than the distance between the two races. The cages keep the sprags equally spaced around the diameter of the races. The springs hold the sprags at the correct angle and maintain contact of the sprags with the races for instantaneous engagement. When a race turns in one direction, the sprags tilt and allow the races to move independently. When a race is moved in the opposite direction, the sprags straighten up and lock the two races together.

10. A band is applied hydraulically by a servo unit. The servo contracts the band when hydraulic pressure pushes against the servo’s piston and overcomes the tension of the servo’s return spring. This action moves an operating rod toward the band, which squeezes the band around the drum.

Fill-in-the-Blanks

1. Sun, ring

2. Double-wrap, single-wrap

3. Governor, throttle, throttle

4. Centrifugal check ball relief

5. Coil, small coil, Belleville

6. Straight, lever, cantilever

7. Driving

8. Surface area

9. Driving device, splined, splined, together, the same speed

10. Reaction members

Multiple Choice

1. C

2. A

3. A

4. C

5. A

6. A

7. C

8. B

9. C

10. C

SHOP MANUAL, PAGES 403-404

ASE-STYLE REVIEW QUESTIONS

1. B

2. C

3. C

4. D

5. C

6. B

7. D

8. A

9. C

10. B

ASE Challenge Questions

1. A

2. C

3. C

4. C

5. A

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