Jeep Grand Cherokee WJ. Manual - part 415

FRONT CLUTCH

DESCRIPTION

The front clutch assembly (Fig. 54) is composed of

the front clutch retainer, pressure plate, four clutch
plates, four driving discs, piston, piston return
spring, return spring retainer, and snap rings. The
front clutch is the forwardmost component in the
transmission geartrain and is directly behind the oil
pump and is considered a driving component.

NOTE: The number of discs and plates may vary
with each engine and vehicle combination.

OPERATION

To apply the clutch, pressure is applied between

With pressure applied between the clutch retainer
and piston, the piston moves away from the clutch
retainer and compresses the clutch pack. This action
applies the clutch pack, allowing torque to flow
through the input shaft into the driving discs, and
into the clutch plates and pressure plate that are
lugged to the clutch retainer. The waved snap ring is
used to cushion the application of the clutch pack. In
some transmissions, the snap ring is selective and
used to adjust clutch pack clearance.

When pressure is released from the piston, the

spring returns the piston to its fully released position
and disengages the clutch. The release spring also
helps to cushion the application of the clutch assem-
bly. When the clutch is in the process of being
released by the release spring, fluid flows through a
vent and one–way ball–check–valve located in the
clutch retainer. The check–valve is needed to elimi-
nate the possibility of plate drag caused by centrifu-
gal force acting on the residual fluid trapped in the
clutch piston retainer.

Fig. 54 Front Clutch

1 – RETAINER HUB SEAL
2 – CLUTCH PISTON
3 – PISTON SPRING
4 – SPRING RETAINER SNAP RING
5 – CLUTCH DISCS
6 – PRESSURE PLATE

7 – SNAP RING (WAVED)
8 – CLUTCH PLATES
9 – SPRING RETAINER
10 – PISTON SEAL
11 – FRONT CLUTCH RETAINER

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DESCRIPTION AND OPERATION (Continued)

REAR CLUTCH

DESCRIPTION

The rear clutch assembly (Fig. 55) is composed of

the rear clutch retainer, pressure plate, three clutch
plates, four driving discs, piston, Belleville spring,
and snap rings. The Belleville spring acts as a lever
to multiply the force applied on to it by the apply pis-
ton. The increased apply force on the rear clutch
pack, in comparison to the front clutch pack, is
needed to hold against the greater torque load
imposed onto the rear pack. The rear clutch is
directly behind the front clutch and is considered a
driving component.

NOTE: The number of discs and plates may vary
with each engine and vehicle combination.

OPERATION

To apply the clutch, pressure is applied between

the clutch retainer and piston. The fluid pressure is
provided by the oil pump, transferred through the
control valves and passageways, and enters the
clutch through the hub of the reaction shaft support.
With pressure applied between the clutch retainer
and piston, the piston moves away from the clutch
retainer and compresses the clutch pack. This action
applies the clutch pack, allowing torque to flow
through the input shaft into the driving discs, and
into the clutch plates and pressure plate that are
lugged to the clutch retainer. The waved snap ring is
used to cushion the application of the clutch pack. In
some transmissions, the snap ring is selective and
used to adjust clutch pack clearance.

Fig. 55 Rear Clutch

1 – PISTON SPRING
2 – REAR CLUTCH PISTON
3 – CLUTCH PISTON SEALS
4 – OUTPUT SHAFT THRUST WASHER (METAL)
5 – INPUT SHAFT SNAP RING
6 – REAR CLUTCH RETAINER
7 – INPUT SHAFT
8 – REAR CLUTCH THRUST WASHER (FIBER)
9 – CLUTCH PACK SNAP RING (SELECTIVE)

10 – TOP PRESSURE PLATE
11 – CLUTCH DISCS (4)
12 – BOTTOM PRESSURE PLATE
13 – WAVE SPRING
14 – CLUTCH PLATES (3)
15 – RETAINER SEAL RING
16 – SHAFT REAR SEAL RING (PLASTIC)
17 – SHAFT FRONT SEAL RING (TEFLON)

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DESCRIPTION AND OPERATION (Continued)

When pressure is released from the piston, the

OVERDRIVE CLUTCH

DESCRIPTION

The overdrive clutch (Fig. 56) is composed of the

pressure plate, two clutch plates, three holding discs,
overdrive piston retainer, piston, piston spacer, and
snap rings. The overdrive clutch is the forwardmost
component in the transmission overdrive unit and is
considered a holding component. The overdrive pis-
ton retainer, piston, and piston spacer are located on
the rear of the main transmission case.

NOTE: The number of discs and plates may vary
with each engine and vehicle combination.

OPERATION

To apply the clutch, pressure is applied between

the piston retainer and piston. The fluid pressure is

provided by the oil pump, transferred through the
control valves and passageways, and enters the
clutch through passages at the lower rear portion of
the valve body area. With pressure applied between
the piston retainer and piston, the piston moves
away from the piston retainer and compresses the
clutch pack. This action applies the clutch pack,
allowing torque to flow through the intermediate
shaft into the overdrive planetary gear set. The over-
drive clutch discs are attached to the overdrive clutch
hub while the overdrive clutch plates, reaction plate,
and pressure plate are lugged to the overdrive hous-
ing. This allows the intermediate shaft to transfer
the engine torque to the planetary gear and overrun-
ning clutch. This drives the planetary gear inside the
annulus, which is attached to the overdrive clutch
drum and output shaft, creating the desired gear
ratio. The waved snap ring is used to cushion the
application of the clutch pack.

Fig. 56 Overdrive Clutch

1 – REACTION PLATE

2 – PRESSURE PLATE

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DESCRIPTION AND OPERATION (Continued)

OVERRUNNING CLUTCH

DESCRIPTION

The overrunning clutch (Fig. 57) consists of an

inner race, an outer race (or cam), rollers and
springs, and the spring retainer. The number of roll-
ers and springs depends on what transmission and
which overrunning clutch is being dealt with.

OPERATION

As the inner race is rotated in a clockwise direction

(as viewed from the front of the transmission), the
race causes the rollers to roll toward the springs,
causing them to compress against their retainer. The
compression of the springs increases the clearance
between the rollers and cam. This increased clear-
ance between the rollers and cam results in a free-
wheeling condition. When the inner race attempts to
rotate counterclockwise, the action causes the rollers
to roll in the same direction as the race, aided by the
pushing of the springs. As the rollers try to move in
the same direction as the inner race, they are
wedged between the inner and outer races due to the
design of the cam. In this condition, the clutch is
locked and acts as one unit.

PLANETARY GEARSET

DESCRIPTION

The planetary gearsets (Fig. 58) are designated as

the front, rear, and overdrive planetary gear assem-
blies and located in such order. A simple planetary
gearset consists of three main members:

• The sun gear which is at the center of the sys-

tem.

• The planet carrier with planet pinion gears

which are free to rotate on their own shafts and are
in mesh with the sun gear.

• The annulus gear, which rotates around and is

in mesh with the planet pinion gears.

NOTE: The number of pinion gears does not affect
the gear ratio, only the duty rating.

OPERATION

With any given planetary gearset, several condi-

tions must be met for power to be able to flow:

• One member must be held.

• Another member must be driven or used as an

input.

• The third member may be used as an output for

power flow.

• For direct drive to occur, two gear members in

the front planetary gearset must be driven.

NOTE: Gear ratios are dependent on the number of
teeth on the annulus and sun gears.

BANDS

DESCRIPTION

KICKDOWN (FRONT) BAND

The kickdown, or “front”, band (Fig. 59) holds the

common sun gear of the planetary gear sets. The
front (kickdown) band is made of steel, and faced on
its inner circumference with a friction–type lining.

Fig. 57 Overrunning Clutch

1 – OUTER RACE (CAM)
2 – ROLLER
3 – SPRING
4 – SPRING RETAINER
5 – INNER RACE (HUB)

Fig. 58 Planetary Gearset

1 – ANNULUS GEAR
2 – SUN GEAR
3 – PLANET CARRIER
4 – PLANET PINIONS (4)

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DESCRIPTION AND OPERATION (Continued)

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