rear differential CHRYSLER TOWN AND COUNTRY 2002 User Guide

DISASSEMBLY
WARNING: Differential is only to be serviced as an
assembly, and no disassembly is required.
(1) Remove six torque arm-to-differential case
bolts and remove torque arm assembly (Fig. 4).
(2) Remove input flange nut and washer using
Tool 6958 and a breaker bar (Fig. 5).(3) Remove input flange (Fig. 6).
(4) Remove input flange seal from overrunning
clutch housing using suitable screwdriver (Fig. 7).
Fig. 4 Torque Arm Fasteners
1 - TORQUE ARM ASSEMBLY
2 - BOLT (SIX)
Fig. 5 Input Flange Nut
1 - INPUT FLANGE
2 - TOOL 6958
Fig. 6 Input Flange
1 - INPUT FLANGE/SHIELD
Fig. 7 Input Flange Seal Removal
1 - INPUT FLANGE SEAL
2 - SCREWDRIVER
3 - 28 REAR DRIVELINE MODULERS
REAR DRIVELINE MODULE (Continued)
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(5) Remove four overrunning clutch housing-to-dif-
ferential assembly bolts (Fig. 8) and remove housing.
(6) Remove front bearing snap ring (Fig. 14).
(7) Remove front bearing (Fig. 14).
(8) Remove o-ring and washer from overrunning
clutch assembly (Fig. 14).
(9) Remove overrunning clutch assembly from vis-
cous coupler (Fig. 9).(10) Remove viscous coupler from differential pin-
ion shaft (Fig. 10).
(11) Remove shim (select) from differential pinion
gear (Fig. 11).
Fig. 8 Overrunning Clutch Housing Bolts
1 - OVERRUNNING CLUTCH HOUSING
2 - BOLT (FOUR)
Fig. 9 Overrunning Clutch
1 - OVERRUNNING CLUTCH
2 - VISCOUS COUPLER
Fig. 10 Viscous Coupler
1 - VISCOUS COUPLER
2 - DIFFERENTIAL PINION
Fig. 11 Shim (Select)
1 - SHIM (SELECT)
2 - DIFFERENTIAL PINION
RSREAR DRIVELINE MODULE3-29
REAR DRIVELINE MODULE (Continued)
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(12) Remove overrunning clutch housing large
o-ring from differential assembly (Fig. 14).
(13) Remove output flanges using suitable screw-
drivers and wood blocks to protect casting (Fig. 12).(14) Remove output flange seals (Fig. 13).
ASSEMBLY
(1) Install output flange seals using tools C4171
and 8493 (Fig. 15).
(2) Install large overrunning clutch housing o-ring
to differential assembly (Fig. 14).
(3) Install shim to differential pinion shaft (Fig.
16).
Fig. 12 Output Flange Removal
1 - WOOD BLOCK
2 - PRYBAR
3 - OUTPUT SHAFT
4 - PRYBAR
5 - WOOD BLOCK
6 - DIFFERENTIAL CASE
Fig. 13 Output Flange Seal Removal
1 - OUTPUT FLANGE SEAL
2 - SCREWDRIVER
3 - 30 REAR DRIVELINE MODULERS
REAR DRIVELINE MODULE (Continued)
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Fig. 14 Drive Line Module
1 - NUT, INPUT FLANGE 6 - BEARING, FRONT 11 - VISCOUS COUPLER
2 - WASHER, INPUT FLANGE NUT 7 - SNAP RING, BEARING RETAINER 12 - O-RING, OVERRUNNING CLUTCH
HOUSING
3 - INPUT FLANGE/SHIELD 8 - O-RING 13 - SHIM (SELECT)
4 - SEAL, INPUT FLANGE 9 - WASHER 14 - DIFFERENTIAL ASSEMBLY
5 - OVERRUNNING CLUTCH HOUSING
BOLT10 - BI-DIRECTIONAL OVERRUNNING
CLUTCH
Fig. 16 Shim (Select)
1 - SHIM (SELECT)
2 - DIFFERENTIAL PINION
Fig. 15 Output Flange Seal Installation
1 - DRIVER HANDLE C4171
2 - INSTALLER 8493
RSREAR DRIVELINE MODULE3-31
REAR DRIVELINE MODULE (Continued)
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(4) Install viscous coupler to differential pinion
shaft (Fig. 17).
(5) Install overrunning clutch assembly to viscous
coupler (Fig. 18).(6) Install washer to overrunning clutch (Fig. 14).
(7) Install o-ring to overrunning clutch (Fig. 14).
(8) Align overrunning clutch ground tab to 12
o'clock position (Fig. 19).
(9) Install overrunning clutch housing into posi-
tion, making sure ground tab engages with notch in
housing (Fig. 20).
Fig. 17 Viscous Coupler
1 - VISCOUS COUPLER
2 - DIFFERENTIAL PINION
Fig. 18 Overrunning Clutch
1 - OVERRUNNING CLUTCH
2 - VISCOUS COUPLER
Fig. 19 Grounding Tab at 12 O'clock
1 - OVERRUNNING CLUTCH
2 - GROUND TAB
Fig. 20 Overrunning Clutch Housing
1 - OVERRUNNING CLUTCH HOUSING
2 - NOTCH
3 - 32 REAR DRIVELINE MODULERS
REAR DRIVELINE MODULE (Continued)
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(10) Install and torque overrunning clutch hous-
ing-to-differential assembly bolts (Fig. 21) to 60 N´m
(44 ft. lbs.).
(11) Install input flange seal using tool 8802 (Fig.
22).(12) Install flange/shield assembly (Fig. 23).
(13) Install input flange washer and nut. Using
tool 6958 (Fig. 24), torque nut to 135 N´m (100 ft.
lbs.).
Fig. 21 Overrunning Clutch Housing Bolts
1 - OVERRUNNING CLUTCH HOUSING
2 - BOLT (FOUR)
Fig. 22 Input Flange Seal Installation
1 - TOOL 8802
2 - HAMMER
Fig. 23 Input Flange/Shield
1 - INPUT FLANGE/SHIELD
Fig. 24 Input Flange Nut
1 - INPUT FLANGE
2 - TOOL 6958
RSREAR DRIVELINE MODULE3-33
REAR DRIVELINE MODULE (Continued)
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(14) Install torque arm assembly into position.
Install and torque torque arm-to-differential assem-
bly bolts (Fig. 25) to 60 N´m (44 ft. lbs.).
INSTALLATION
(1) Install rear driveline module assembly to
transmission jack and secure.
(2) Raise rear driveline module into position and
install and torque mounting bolts (Fig. 26) to 54 N´m
(40 ft. lbs.).(3) Remove transmission jack.
(4) Install and torque torque arm mount-to-body
bolts to 54 N´m (40 ft. lbs.).
(5) Install halfshafts to differential output flanges
and torque bolts (Fig. 27) to 61 N´m (45 ft. lbs.).
(6) Install propeller shaft. (Refer to 3 - DIFFER-
ENTIAL & DRIVELINE/PROPELLER SHAFT -
INSTALLATION)
(7) Lower vehicle.
Fig. 25 Torque Arm Fasteners
1 - TORQUE ARM ASSEMBLY
2 - BOLT (SIX)
Fig. 26 Rear Drive Line Module Assembly Rear
Mounting Bolts
1 - DRIVELINE MODULE RETAINING BOLT (2)
2 - RUBBER ISOLATOR
3 - WASHER
Fig. 27 Half Shaft Mounting Bolts
1 - SHAFT
2 - FLANGE
3 - 34 REAR DRIVELINE MODULERS
REAR DRIVELINE MODULE (Continued)
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SPECIFICATIONS - REAR DRIVELINE MODULE
TORQUE SPECIFICATIONS
DESCRIPTION N´m Ft. Lbs. In. Lbs.
Bolt, Driveline Module-to-Body 54 40 Ð
Bolt, Halfshaft-to-Ouput Flange 61 45 Ð
Bolt, Overrunning Clutch Housing-to-Differential 60 44 Ð
Bolt, Torque Arm-to-Differential Assembly 60 44 Ð
Bolt, Torque Arm Mount-to-Body 54 40 Ð
Nut, Input Flange 135 100 Ð
Plug, Differential Drain/Fill 35 26 Ð
Plug, Overrunning Clutch Housing Drain/Fill 30 22 Ð
Vent, Differential/Overrunning Clutch Housing 12 Ð 110
SPECIAL TOOLS
Tool 6958
Tool 8493
Tool 8802
RSREAR DRIVELINE MODULE3-35
REAR DRIVELINE MODULE (Continued)
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BI-DIRECTIONAL
OVERRUNNING CLUTCH
DESCRIPTION
The bi-directional overrunning clutch (BOC) (Fig.
28) works as a mechanical disconnect between the
front and rear axles, preventing torque from being
transferred from the rear axle to the front. The BOC
is a simply an overrunning clutch which works in
both clockwise and counter-clockwise rotations. This
means that when the output (the rear axle) is rotat-
ing faster in one direction than the input (front axle),
there is no torque transmission. But when the input
speed is equal to the output speed, the unit becomes
locked. The BOC provides significant benefits regard-
ing braking stability, handling, and driveline durabil-
ity. Disconnecting the front and the rear driveline
during braking helps to maintain the braking stabil-
ity of an AWD vehicle. In an ABS/braking event, the
locking of the rear wheels must be avoided for stabil-
ity reasons. Therefore brake systems are designed to
lock the front wheels first. Any torque transfer from
the rear axle to the front axle disturbs the ABS/brak-
ing system and causes potential instabilities on aslippery surface. The BOC de-couples the rear driv-
eline as soon the rear wheels begin to spin faster
than the front wheels (front wheels locked) in order
to provide increased braking stability. Furthermore
the BOC also reduces the likelihood of throttle off
over-steer during cornering. In a throttle off maneu-
ver, the BOC once again de-couples the rear driveline
forcing all the engine brake torque to the front
wheels. This eliminates the chance of lateral slip on
the rear axle and increases it on the front. The vehi-
cle will therefore tend to understeer, a situation
which is considered easier to manage in most circum-
stances. During this maneuver, and during the ABS
braking event, the BOC does not transmit torque
through to the rear wheels. The rear driveline mod-
ule, with the BOC, will perform the same as a front
wheel drive vehicle during these events. The gear
ratio offset between the front and rear differentials
force the BOC into the overrunning mode most of the
time. This allows BOC to significantly reduce the
rolling resistance of the vehicle, which improves fuel
consumption, allows the downsizing of the driveline
components, and prevents the PTU and propshaft
joints from overheating.
3 - 36 REAR DRIVELINE MODULERS
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OPERATION
In order to achieve all-wheel drive operation in
reverse, the overrunning clutch locking functional direc-
tion must be reversible. The bi-directional overrunning
clutch (BOC) changes the operational mode direction
depending on the propeller shaft direction. The propel-
ler shaft rotates in the clockwise (when viewed from the
front) direction when the vehicle is moving forward,
which indexes the BOC to the forward overrunning
position. When the vehicle is in reverse, the propeller
shaft will rotate counter-clockwise and index the BOC
to the reverse overrunning position.
The BOC acts as a mechanical stator. It is active
(transmitting torque), or it is not active and in over-
running mode (not transmitting torque). This ªall or
nothingº approach to torque transfer would cause a
sudden application of all available power to the rear
wheels, which is not desirable. Therefore it is run in
series with a viscous coupler to smooth, dampen, and
limit the transmission of torque to the rear axle and
to prevent a step style torque input to the rear axle.
STEADY STATE, LOW TO MODERATE SPEED, NO
FRONT WHEEL SLIP, FORWARD DIRECTION
During normal driving conditions, (no wheel slip), the
inner shaft (front axle) and outer race (viscous coupler)
are running at different speeds due to the different gear
ratios between the front and rear differentials. In this
condition, the outer race is always spinning faster (over-
driving between 5-32 rpm) than the inner shaft. When
the BOC (Fig. 29) is running under these conditions, at
low vehicle speeds the drag shoes and the cage keep the
rollers up on the left side (forward side) of the inner
shaft flats. This is what is known as ªoverrunning
mode.º Notice that when the clutch is in overrunning
mode, the rollers are spinning clockwise and with the
outer race, thus no torque is being transferred.
NOTE: Low speed, forward and reverse operation is
identical, just in opposite directions. (Fig. 29) shows
forward direction in reverse the rollers are on the other
side of the flats due to a reversal of the cage force.
TRANSIENT CONDITION (BOC LOCKED), FRONT
WHEEL SLIP, FORWARD DIRECTION
When the front wheels lose traction and begin to
slip, the propeller shaft and rear axle pinion speed
difference decreases to zero. At this point the input
shaft (cam) becomes the driving member of the BOC
(Fig. 30), compressing the rollers against the outer
race. This locks the input shaft with the outer race
and transmits torque to the housing of the viscous
coupler, that in turn transmits torque to the rear
axle pinion. It should also be noted that when the
device is locked, the inner shaft and the outer raceare rotating at the same speed. The rollers are
pinched at this point and will stay locked until a
torque reversal (no front wheel slip) occurs. When
locked, the viscous coupler slips during the torque
transfer and the amount of torque transferred is
dependent on the coupling characteristic and the
amount of front wheel slip.
Fig. 29 BOC Operation at Low Speeds With No
Front Wheel Slip
1 - CAGE
2 - ROLLER
3 - INPUT SHAFT
Fig. 30 BOC Operation with Front Wheel Slip
3 - 38 REAR DRIVELINE MODULERS
BI-DIRECTIONAL OVERRUNNING CLUTCH (Continued)
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