2. OBJECTIVES After studying Chapter 4, the reader should be able to:
Describe the power flow through a planetary gearset.
Identify the components of a multiple-disc clutch and describe how it operates.
Identify a one-way clutch and describe how it operates.
Identify a band and servo and describe how they operate.

3. INTRODUCTION
There are several paths for power to flow through an automatic transmission, and each path provides a different gear ratio.
These power paths are controlled by the driving and reaction devices, also called driving and reaction members.
The driving devices connect the turbine shaft from the torque converter to a member of the planetary gear train.
The reaction devices connect a member of the gear train to the transmission case.

4. INTRODUCTION
FIGURE 4-1 The 4L60 (THM 700) has one band, five multiple-disc clutches, and two one-way clutches to control the power flow. The reverse input, overrun, forward, and 3–4 clutches along with the forward sprag clutch are driving members. The 2–4 band, low roller clutch, and low-reverse clutch are reaction members.

5. DRIVING DEVICES The driving devices provide the input to the gearset.
The turbine shaft is normally built as part of or splined to one or more of the driving devices.
Driving devices are usually multiple-plate disc clutches.
In most cases, they will be at the front of the transmission, just behind the pump.

6. DRIVING DEVICES
An example of this involves the two clutches in front of a Simpson gear train transmission.
Chrysler Corporation calls the first clutch the front clutch;
Ford Motor Company calls it a high-reverse clutch;
General Motors Corporation and Toyota call it a direct clutch;
Toyota uses the term direct clutch but more commonly calls it C2.
Synchronizing Shifts
Synchronous
Nonsynchronous

7. MULTIPLE-DISC DRIVING CLUTCHES
The parts of a clutch assembly are: the drum, hub, lined plates, unlined plates, pressure plate, apply piston, and piston return springs.
The drum, also called a housing, has splines inside its outer edge for the externally lugged plates, usually the unlined plates.
The inner diameter of the drum is machined for the apply piston and its inner and outer seals.

8. MULTIPLE-DISC DRIVING CLUTCHES
FIGURE 4-2 A sectioned view (a) and exploded view (b) of a multiple-disc clutch. Note the piston to apply the clutch and the spring(s) to release it. (b is courtesy of Chrysler Corporation)

9. MULTIPLE-DISC DRIVING CLUTCHES
FIGURE 4-3 A 4L60 input clutch assembly has three separate clutch packs:202 is the overrun clutch; 607 is the forward clutch; and 228 is the 3–4 clutch. The input sprag assembly is at the bottom left. (Courtesy of Slauson Transmission Parts,

10. MULTIPLE-DISC DRIVING CLUTCHES
FIGURE 4-4 The apply piston is released (left) by the coil springs. Fluid pressure moves the piston to apply the clutch (right).

11. MULTIPLE-DISC DRIVING CLUTCHES
FIGURE 4-5 Clutch piston return springs can be a single large spring (a), a group of small springs (b), or a single Belleville spring (c). (Courtesy of Chrysler Corporation)

12. MULTIPLE-DISC DRIVING CLUTCHES
Clutch Plates
Double- and Single-Sided Friction Plates
Clutch Operation
Wet Friction
Open Pack Drag

13. MULTIPLE-DISC DRIVING CLUTCHES
FIGURE 4-6 Any fluid left in the apply chamber of a spinning clutch will be pushed outward by centrifugal force. This force can cause the fluid to push on the piston and partially apply a clutch.
FIGURE 4-7 A close-up view of the surface finish on a steel plate. Note the small nicks and grooves that tend to hold fluid.

14. MULTIPLE-DISC DRIVING CLUTCHES
FIGURE 4-8 Friction plates often have a groove pattern to help wipe fluid away, dissipate heat, eliminate clutch noise, and change friction qualities during apply and release. A smooth plate is the coolest and slowest to apply; the waffle plate will apply the fastest, but it will have less heat removed by the oil. (Courtesy of Raybestos)

15. MULTIPLE-DISC DRIVING CLUTCHES
FIGURE 4-9 This friction plate has directional grooves. The lugs (center inset) are assymmetrical, so the plate cannot be installed incorrectly. (Courtesy of Raybestos)

16. MULTIPLE-DISC DRIVING CLUTCHES
FIGURE 4-10 A microscopic view of the surface of paper friction plate lining. Friction material is formed on the lined plate to establish a crosslinked matrix. Note the large cavities between the paper fibers that can store relatively large amounts of fluid. (Courtesy of Raybestos)

17. MULTIPLE-DISC DRIVING CLUTCHES
FIGURE 4-11 In this clutch assembly, clutch stack clearance is adjusted using either the large or small flange (backing plate). Other clutches may use a selective snap ring. (Courtesy of Toyota Motor Sales USA, Inc.)

18. MULTIPLE-DISC DRIVING CLUTCHES
FIGURE 4-12 The ZPAK is a single-sided clutch design (a). Both sides of the two different plates show a lined and unlined side (b). The clutch pack requires proper placement of the end plates (c). (Courtesy of Raybestos)

19. MULTIPLE-DISC DRIVING CLUTCHES
FIGURE 4-13 When this transmission is in first gear, the sun gear and unlined plates of the front clutch rotate counterclockwise while the hub and lined plates of this clutch rotate clockwise. Any drag will produce heat that can cause clutch burnout.

20. MULTIPLE-DISC DRIVING CLUTCHES
FIGURE 4-14 If you push against a stationary book, you will notice the static friction that resists motion. Pushing against the same book while it is sliding is easier because the dynamic friction is somewhat less.

21. MULTIPLE-DISC DRIVING CLUTCHES
FIGURE 4-15 A comparison of the dynamic and static coefficients of friction with motor oil and three types of ATF. (Courtesy of Raybestos)

22. MULTIPLE-DISC DRIVING CLUTCHES
FIGURE 4-16 The clutch apply curves of five different clutches. The dynamic friction is the rate of torque increase, whereas the static friction is the amount of torque at the left. (Courtesy of AFM)

23. MULTIPLE-DISC DRIVING CLUTCHES
FIGURE 4-17 The four slots in this steel plate, called a turbulator plate, promote a fluid layer on each side of the stationary plate. (Courtesy of Raybestos)

24. ONE-WAY DRIVING CLUTCHES
Two styles of one-way clutches are used in automatic transmissions:
Roller clutches
Sprag clutches
Mechanical Diode
Clutch Operation

25. ONE-WAY DRIVING CLUTCHES
FIGURE 4-18 This overrunning clutch assembly is a roller clutch with the clutch cam secured to the transmission case (a). It uses a set of springloaded rollers in the retainer (b). (Courtesy of Chrysler Corporation)

26. ONE-WAY DRIVING CLUTCHES
FIGURE 4-19 If this inner race tries to turn counterclockwise, the rollers will wedge at the narrow part of the cams and lock the clutch. Movement of the inner race in a clockwise direction will move the rollers to the wide part of the cams, where they will roll freely. (Courtesy of Chrysler Corporation)

27. ONE-WAY DRIVING CLUTCHES
FIGURE 4-20 Each sprag has a major and minor diameter. The major diameter is greater than the distance between the two races (right); the minor diameter is smaller (left). (Courtesy of Toyota Motor Sales USA, Inc.)

28. ONE-WAY DRIVING CLUTCHES
FIGURE 4-21 A mechanical diode. The struts can move out of the pocket plate to engage the notch plate, and this will lock the pocket plate. The pocket plate can overrun in the opposite direction.

29. ONE-WAY DRIVING CLUTCHES
FIGURE 4-22 This clutch hub and sprag clutch should rotate freely in a clockwise direction but should lock up in the opposite direction. (Courtesy of Toyota Motor Sales USA, Inc.)

30. HOLDING/REACTION DEVICES
A holding member acts as a brake to hold a planetary gearset member in reaction.
Three types of holding devices are used:
Multiple-disc clutches
Bands
One-way clutches

31. MULTIPLE-DISC HOLDING CLUTCHES
A multiple-disc holding clutch is quite similar to a driving clutch.
The difference is the transmission case is the drum, and the clutch plates splined to it do not rotate.
Some manufacturers call these clutches a brake.
The lugs on the outside of the unlined plates fit into slots built into the case.

32. MULTIPLE-DISC HOLDING CLUTCHES
FIGURE 4-23 The 41TE transaxle low/reverse clutch is a holding clutch. Note the splines in the case for the clutch plates. (Courtesy of Chrysler Corporation)

33. MULTIPLE-DISC HOLDING CLUTCHES
FIGURE 4-24 The plates of the O/D brake are splined to the transaxle O/D case. The first and reverse brake and the second brake are multiple-disc clutches that are splined to the transaxle case. (Courtesy of Toyota Motor Sales USA, Inc.)

34. ONE-WAY HOLDING CLUTCHES
One-way clutches are commonly used as reaction devices.
The outer race is often secured directly to the transmission case so it cannot rotate.

35. BANDS
A band is a circular strip of metal that has lining bonded to the inner surface.
It wraps around the smooth surface of a drum.
There are three types:
Single thick, heavy band
Single thin, light band
Split, double-wrap, heavy band

36. BANDS
FIGURE 4-25 A flex band (a) and a rigid band (b). Note the flex band has circumferential grooves for improved conformity, fluid flow, and performance. Note that this is a double-wrap rigid band. Single-wrap rigid bands are also used. (Courtesy of Raybestos)

37. BANDS
FIGURE 4-26 This band uses an adjustable anchor that allows the clearance to be easily adjusted. (Courtesy of Chrysler Corporation)

38. BANDS
FIGURE 4-27 A band is normally anchored at the trailing end so its rotation will pull the band tighter. Note that this servo is applied by fluid pressure and released by a spring. (Courtesy of Toyota Motor Sales USA, Inc.)

39. BANDS
FIGURE 4-28 Fluid pressure acting on the piston forces the piston and piston rod inward to apply the band. The band is released by the outer spring pushing outward on the piston. (Courtesy of Toyota Motor Sales USA, Inc.)

40. BANDS
FIGURE 4-29 This band apply lever increases servo force by about two and a half times. The apply speed will be decreased the same amount because the servo must travel a greater distance. (Courtesy of Chrysler Corporation)

41. BANDS
FIGURE 4-30 Air pressure can be used to apply the band while the length of the piston stroke is measured. Piston stroke is used to determine the correct piston rod and adjust band clearance. (Courtesy of Toyota Motor Sales USA, Inc.)

42. BANDS
Band Operation
When fluid pressure enters the servo, the servo piston strokes to tighten the band around the drum.
The amount of torque that a band can absorb before slipping is determined by the band-to-drum contact area, type of band, drum diameter, fluid type, and the force squeezing the band onto the drum.

43. BANDS
FIGURE 4-31 This band is applied when 1–2 shift valve pressure pushes upward on the servo piston. It will release when 2–3 shift valve pressure pushes the piston downward. Note the larger area above the piston.

44. SHIFT QUALITY
As a power shift occurs, there must be a smooth transition from one apply device to the next.
The smoothness of the shift is referred to as shift quality or shift feel.

45. SHIFT QUALITY
FIGURE 4-32 In second gear, the sun gear and front clutch drum are held stationary by the band (a). In third gear, the clutch is applied so drum and sun gear are rotating at engine speed (b). The driver feels this change as shift quality. (Courtesy of Nissan North America, Inc.)

46. SHIFT QUALITY
FIGURE 4-33 Two cushion plates: the Belleville plate has a coned shape. The wave plate has a wavy shape. Both of them will flatten slightly as the clutch is applied.

47. SHIFT QUALITY Shifts Involving One-Way Clutches
Deceleration with One-Way Clutches
FIGURE 4-34 This one-way clutch allows the shaft to overrun in a clockwise direction. (Courtesy of Toyota Motor Sales USA, Inc.)

48. SUMMARY
The power flow through a gearset is controlled by driving and reaction devices.
The driving and reaction devices are multiple-disc clutches, one-way clutches, and bands.
Multiple-disc clutches are the primary driving devices and are also used to hold planetary members in reaction.
One-way clutches primarily are used to hold planetary members in reaction, but can be used with a multipledisc clutch to be a driving device.
Bands are used to hold a planetary member in reaction.
The timing of the apply and release of the apply devices has a direct effect on shift quality.

49. REVIEW QUESTIONS
The power flow through an automatic transmission is controlled by the _________ and _________ devices.
The most common driving member is the _________ _________ _________; a(n) _________ _________ is also used as a driving member.
List the seven major parts of a clutch assembly.
Usually the lined plates of a driving multiple-disc clutch are splined to the clutch _________, and the unlined plates are splined to the clutch _________.
List the four types of return springs used in a multiple-disc clutch are.

50. REVIEW QUESTIONS
Piston travel or clutch plate clearance can be adjusted by replacing the _________ or _________.
The multiple-disc clutch torque capacity can be increased by increasing the _________ area, number of _________, _________ size, or by increasing the _________ pressure.
Shift quality is a term used to describe the _________ of a shift.
The two types of one-way clutches used in an automatic transmission are the _________ and _________.
One-way clutches _________ when turned in one direction and _________ when rotated in the other direction.

51. REVIEW QUESTIONS
One-way clutches can be used as a _________ or a _________ apply device.
List the three types of apply devices that can be used to hold a planetary member.
A one-way clutch that is holding is referred to as being _________.
A multiple-disc clutch that is used in reaction has the steel plates splined to the _________.
Bands are applied by _________ pressure and released by _________ or _________ pressure.

52. REVIEW QUESTIONS
A _________ shift sequence is a shift where the apply and release of the apply devices must be carefully timed.
A shift sequence that does not need to be timed is known as a _________ or _________ shift.
One-way clutches are only used in the _________ gear ranges.
The disadvantage of one-way clutches is that they do not provide _________ on deceleration.
Manual gear ranges use an additional _________ or _________ to provide more holding power when pulling a heavy load.

53. CHAPTER QUIZ
Student A says that in order for a planetary gearset to change the ratio and transmit torque, there must be an input and a reaction member. Student B says that the turbine shaft is the primary input to the transmission. Who is correct?
Student A
Student B
Both A and B
Neither A nor B

54. CHAPTER QUIZ
Student A says that in order for a planetary gearset to change the ratio and transmit torque, there must be an input and a reaction member. Student B says that the turbine shaft is the primary input to the transmission. Who is correct?
Student A
Student B
Both A and B
Neither A nor B

55. CHAPTER QUIZ
2. Student A says that neutral in a planetary gearset can be obtained by releasing all of the driving clutches. Student B says that neutral in a planetary gearset can be obtained by not applying any reaction members. Who is correct?
Student A
Student B
Both A and B
Neither A nor B

56. CHAPTER QUIZ
2. Student A says that neutral in a planetary gearset can be obtained by releasing all of the driving clutches. Student B says that neutral in a planetary gearset can be obtained by not applying any reaction members. Who is correct?
Student A
Student B
Both A and B
Neither A nor B

57. CHAPTER QUIZ
3. The apply device that is most commonly used as a driving member is a
cone clutch.
multiple-disc clutch.
one-way clutch.
band.

58. CHAPTER QUIZ
3. The apply device that is most commonly used as a driving member is a
cone clutch.
multiple-disc clutch.
one-way clutch.
band.

59. CHAPTER QUIZ
4. Student A says that some of the plates used in a multiple-disc clutch are lined with paper friction material. Student B says that some of the plates used in a multiple-disc clutch are unlined steel plates. Who is correct?
Student A
Student B
Both A and B
Neither A nor B

60. CHAPTER QUIZ
4. Student A says that some of the plates used in a multiple-disc clutch are lined with paper friction material. Student B says that some of the plates used in a multiple-disc clutch are unlined steel plates. Who is correct?
Student A
Student B
Both A and B
Neither A nor B

61. CHAPTER QUIZ 5. The ideal unlined steel plates _________.
are perfectly flat
have many very small nicks in their surface
are not extremely smooth
All of these

62. CHAPTER QUIZ 5. The ideal unlined steel plates _________.
are perfectly flat
have many very small nicks in their surface
are not extremely smooth
All of these

63. CHAPTER QUIZ
6. The most common material that the friction plate lining is made from is _________.
Paper
Asbestos
inorganic fibers
Any of these

64. CHAPTER QUIZ
6. The most common material that the friction plate lining is made from is _________.
Paper
Asbestos
inorganic fibers
Any of these

65. CHAPTER QUIZ 7. A multiple-disc clutch is applied by _________.
one or more coil springs
a piston and air pressure
hydraulic pressure pushing against a piston
None of these

66. CHAPTER QUIZ 7. A multiple-disc clutch is applied by _________.
one or more coil springs
a piston and air pressure
hydraulic pressure pushing against a piston
None of these

67. CHAPTER QUIZ
The grooves in the surface of a lined clutch plate _________.
help cool the friction material
allow oil to flow between the plates more easily
are cut using different patterns depending on the clutch
All of these

68. CHAPTER QUIZ
The grooves in the surface of a lined clutch plate _________.
help cool the friction material
allow oil to flow between the plates more easily
are cut using different patterns depending on the clutch
All of these

69. CHAPTER QUIZ
9. The torque-carrying capacity of a clutch is determined by the _________.
number of plates
amount of lining area on the plates
amount of pressure squeezing the plates together
All of these

70. CHAPTER QUIZ
9. The torque-carrying capacity of a clutch is determined by the _________.
number of plates
amount of lining area on the plates
amount of pressure squeezing the plates together
All of these

71. CHAPTER QUIZ
10. Commonly used holding or reaction members are _________.
Bands
one-way clutches
multiple-disc clutches
All of these

72. CHAPTER QUIZ
10. Commonly used holding or reaction members are _________.
Bands
one-way clutches
multiple-disc clutches
All of these

73. CHAPTER QUIZ
11. Student A says that a band is applied by a hydraulic servo and released by a spring or hydraulic pressure. Student B says that a clutch is applied by hydraulic pressure and released by a spring or hydraulic pressure. Who is correct?
Student A
Student B
Both A and B
Neither A nor B

74. CHAPTER QUIZ
11. Student A says that a band is applied by a hydraulic servo and released by a spring or hydraulic pressure. Student B says that a clutch is applied by hydraulic pressure and released by a spring or hydraulic pressure. Who is correct?
Student A
Student B
Both A and B
Neither A nor B

75. CHAPTER QUIZ
12. When a multiple-disc clutch is used as a holding member, the lugs of the unlined plates are splined into _________.
a very large drum
the reaction carrier
the transmission case
the output shaft

76. CHAPTER QUIZ
12. When a multiple-disc clutch is used as a holding member, the lugs of the unlined plates are splined into _________.
a very large drum
the reaction carrier
the transmission case
the output shaft

77. CHAPTER QUIZ 13. The strongest of the band designs is the _________.
single wrap
heavy band
double wrap
flexible

78. CHAPTER QUIZ 13. The strongest of the band designs is the _________.
single wrap
heavy band
double wrap
flexible

79. CHAPTER QUIZ 14. Band clearance can be adjusted using a _________.
threaded adjuster at the band anchor
threaded adjuster at the servo lever
selective sized servo piston rod
Any of these, depending on the transmission

80. CHAPTER QUIZ 14. Band clearance can be adjusted using a _________.
threaded adjuster at the band anchor
threaded adjuster at the servo lever
selective sized servo piston rod
Any of these, depending on the transmission

81. CHAPTER QUIZ
15. Student A says that the inner and outer races of a sprag clutch are perfectly round and smooth. Student B says that one of the races of a roller clutch is perfectly round and smooth while the other one has a series of ramps in it. Who is correct?
Student A
Student B
Both A and B
Neither A nor B

82. CHAPTER QUIZ
15. Student A says that the inner and outer races of a sprag clutch are perfectly round and smooth. Student B says that one of the races of a roller clutch is perfectly round and smooth while the other one has a series of ramps in it. Who is correct?
Student A
Student B
Both A and B
Neither A nor B

83. CHAPTER QUIZ 16. When a sprag clutch locks, the sprags _________.
try to rotate but wedge between the two races
roll down the ramps and wedge into place
rotate into a position that unlocks them
rotate with the free or rotating race

84. CHAPTER QUIZ 16. When a sprag clutch locks, the sprags _________.
try to rotate but wedge between the two races
roll down the ramps and wedge into place
rotate into a position that unlocks them
rotate with the free or rotating race

85. CHAPTER QUIZ 17. When a roller clutch unlocks, the rollers _________.
are wedged between the two races
rotate between the two races like a series of bearing rollers
rotate to a position where they allow both inner and outer races to rotate
None of these

86. CHAPTER QUIZ 17. When a roller clutch unlocks, the rollers _________.
are wedged between the two races
rotate between the two races like a series of bearing rollers
rotate to a position where they allow both inner and outer races to rotate
None of these

87. CHAPTER QUIZ A one-way clutch in a reverse direction _________.
is applied by hydraulic pressure
is released by a group of springs
self-applies whenever one of the races tries to rotate in a reverse direction
Any of these

88. CHAPTER QUIZ A one-way clutch in a reverse direction _________.
is applied by hydraulic pressure
is released by a group of springs
self-applies whenever one of the races tries to rotate in a reverse direction
Any of these

89. CHAPTER QUIZ
19. The term used to describe when the apply devices do not need to be timed when shifting gears is _________.
shift feel
Asynchronous
shift quality
All of these

90. CHAPTER QUIZ
19. The term used to describe when the apply devices do not need to be timed when shifting gears is _________.
shift feel
Asynchronous
shift quality
All of these

91. CHAPTER QUIZ
20. The term used to describe the condition when the engine is used to slow the vehicle is _________.
compression braking
compression gear
low gear
forced braking

92. CHAPTER QUIZ
20. The term used to describe the condition when the engine is used to slow the vehicle is _________.
compression braking
compression gear
low gear
forced braking