torque DODGE TOWN AND COUNTRY 2001 Workshop Manual

adjustment, maintenance or fluid checks required
during the life of the unit.
The overrunning clutch allows the rear wheels to
overrun the front wheels during a rapid front wheel
lock braking maneuver. The overrunning action pre-
vents any feed-back of front wheel braking torque to
the rear wheels. It also allows the braking system to
control the braking behavior as a two wheel drive
(2WD) vehicle.
The overrunning clutch housing has a separate oil
sump and is filled independently from the differen-
tial. The fill plug is located on the side of the over-
running clutch case. When filling the overrunning
clutch with lubricant use MopartATF+4 (Automatic
Transmission FluidÐType 9602) or equivalent.
The differential assembly contains a conventional
open differential with hypoid ring gear and pinion
gear set. The hypoid gears are lubricated by SAE
80W-90 gear lubricant.DIAGNOSIS AND TESTING - REAR DRIVELINE
MODULE NOISE
Different sources can be the cause of noise that the
rear driveline module assembly is suspected of mak-
ing. Refer to the following causes for noise diagnosis.
DRIVELINE MODULE ASSEMBLY NOISE
The most important part of driveline module ser-
vice is properly identifying the cause of failures and
noise complaints. The cause of most driveline module
failures is relatively easy to identify. The cause of
driveline module noise is more difficult to identify.
If vehicle noise becomes intolerable, an effort
should be made to isolate the noise. Many noises that
are reported as coming from the driveline module
may actually originate at other sources. For example:
Fig. 1 AWD Driveline Module Assembly
1 - TORQUE ARM
2 - INPUT FLANGE
3 - FLANGE NUT
4 - WASHER
5 - SHIELD
6 - VENT
7 - O-RING
8 - WASHER
9 - BI-DIRECTIONAL OVERRUNNING CLUTCH (BOC)
10 - VISCOUS COUPLER11 - SHIM (SELECT)
12 - O-RING
13 - DIFFERENTIAL ASSEMBLY
14 - PLUG-DIFFERENTIAL FILL
15 - PLUG-OVERRUNNING CLUTCH HOUSING DRAIN
16 - SNAP RING
17 - BEARING
18 - OVERRUNING CLUTCH HOUSING
19 - SEAL-INPUT FLANGE
RSREAR DRIVELINE MODULE3-27
REAR DRIVELINE MODULE (Continued)
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DIAGNOSIS AND TESTING - REAR DRIVELINE
MODULE OPERATION
Driveline module operation requires relatively
straight-forward diagnosis. Refer to the following
chart:
DRIVELINE MODULE DIAGNOSIS CHART
CONDITION POSSIBLE CAUSES CORRECTION
Rear wheels not
overrunning1) Bi-directional overrunning clutch
failure1) Replace overrunning clutch
components as required
No AWD in forward or
reverse directions, propeller
shaft turning1) Bi-directional overrunning clutch
failure1) Replace overrunning clutch
components as required
2) Viscous coupling failure 2) Replace viscous coupling
3) Rear differential failure 3) Replace the rear differential
assembly
No AWD in forward or
reverse directions, propeller
shaft not turning1) Power transfer unit failure. 1) Replace power transfer unit
components as necessary
Vibration at all speeds,
continuous torque transfer1) Mis-matched tires, worn tires on
front axle.1) Replace worn or incorrect
(mis-matched) tires with same
make and size
REMOVAL
(1) Raise vehicle on hoist.
(2) Drain fluid from overrunning clutch housing
and/or differential assembly if necessary.
(3) Remove propeller shaft. (Refer to 3 - DIFFER-
ENTIAL & DRIVELINE/PROPELLER SHAFT -
REMOVAL)
(4) Disconnect left and right rear halfshafts from
output flanges (Fig. 2).(5) Remove torque arm mount to body bolts.
(6) Position transmission jack to driveline module
assembly and secure assembly to jack.
(7) Remove two driveline module-to-body bolts
(Fig. 3).
(8) Lower driveline module from vehicle and
remove from jack.
Fig. 2 Half Shaft Mounting Bolts
1 - SHAFT
2 - FLANGE
Fig. 3 Rear Drive Line Module Assembly Mounting
Bolts
1 - DRIVELINE MODULE RETAINING BOLT (2)
2 - RUBBER ISOLATOR
3 - WASHER
RSREAR DRIVELINE MODULE3-29
REAR DRIVELINE MODULE (Continued)
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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).
(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).
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 - 30 REAR DRIVELINE MODULERS
REAR DRIVELINE MODULE (Continued)
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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).
(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).
(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.).
(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.).
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 - 32 REAR DRIVELINE MODULERS
REAR DRIVELINE MODULE (Continued)
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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 - 36 REAR DRIVELINE MODULERS
REAR DRIVELINE MODULE (Continued)
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SPECIFICATIONS
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-
Differential60 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
Housing12 Ð 110
SPECIAL TOOLS
SPECIAL TOOLS
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
Tool 6958
Tool 8493
Tool 8802
RSREAR DRIVELINE MODULE3-37
REAR DRIVELINE MODULE (Continued)
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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 a
slippery 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.
OPERATION
In order to achieve all-wheel drive operation in
reverse, the overrunning clutch locking functional
direction must be reversible. The bi-directional over-
running clutch (BOC) changes the operational mode
direction depending on the propeller shaft direction.
The propeller shaft rotates in the clockwise (when
viewed from the front) direction when the vehicle is
moving forward, which indexes the BOC to the for-
ward overrunning position. When the vehicle is in
reverse, the propeller shaft will rotate counter-clock-
wise 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 dif-
ferentials. In this condition, the outer race is always
spinning faster (overdriving 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 race
are 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.
3 - 38 REAR DRIVELINE MODULERS
BI-DIRECTIONAL OVERRUNNING CLUTCH (Continued)
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To keep the rollers in the overrunning position and
avoid undesired9high speed lockup9, a high speed
latch (Fig. 33) positions the cage before the ground
shoes lift off. A further explanation of the high speed
effects follows as well. Utilizing only the friction
shoes approach means that at high speed the
required ground shoe drag torque would cause exces-
sive brake shoe wear or the roller will begin to
migrate to the opposite side of the flat due to the
drag force of the outer race. This would result in sys-
tem lock-up. (Fig. 34) shows the BOC as it crosses
the speed where the brake shoe force is overcome by
the roller drag on the outer race. Notice that the
roller is locking up on the opposite side of the flat
and the cage supplies no force on the rollers.
This lock-up is not desired, and requires the use of
another mechanism to prevent the lock-up. The
device that prevents undesired high-speed lock-up is
called a9high speed latch9.
Similar to the friction shoes, the two-piece high-
speed latch will separate from each other at high
rotational speeds due to centrifugal effects. (Fig. 35)
shows the high speed latch engaged. The gap9x9
increases with speed, eventually locking into one of
the slots in the BOC shaft. When the high-speed
latch is activated (propeller shaft speed reaches X
amount), the cage is partially fixed, and cannot lock
on the wrong side of the flat as shown (Fig. 34). Thehigh speed latch is a one way device and does not
prevent high-speed lockup in the reverse direction. At
high speeds, the BOC provides the same function as
low speeds, transferring torque to the viscous coupler
only when front wheel slip overcomes the axle ratio
offset.
At high speed, the rollers are forced outward to the
outer race because of centrifugal force. At high
speeds, the friction shoes can no longer prevent lock-
up. When the teeth on the high-speed latch engage
into the input shaft, it keeps the rollers centered
above the flats because the tabs on the latch are
locked into the cage. (Fig. 36) shows the roller config-
uration with the High-Speed Latch engaged.
On the BOC shaft, the high speed latch teeth lock
up in the grooved areas, shown in (Fig. 37), when the
turning speed reaches the critical value. (Fig. 37)
also shows the outer race/viscous coupler. Notice the
surface (outer race) the rollers mate against when
transferring torque.
Fig. 32 Location of the Grounding Element
1 - DIFFERENTIAL HOUSING
2 - GROUND TAB
3 - GARTER SPRING
Fig. 33 BOC High Speed Latch (Not Engaged)
1 - TOOTH (TWO PLACES)
2 - GARTER SPRING
3 - TABS AT BOTH ENDS FIT INTO SLOTS IN CAGE
4 - TWO PART DESIGN
RSREAR DRIVELINE MODULE3-41
BI-DIRECTIONAL OVERRUNNING CLUTCH (Continued)
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DIFFERENTIAL ASSEMBLY
DESCRIPTION
The differential gear system divides the torque
between the axle shafts. It allows the axle shafts to
rotate at different speeds when turning corners.
Each differential side gear is splined to an axle
shaft. The pinion gears are mounted on a pinion
mate shaft and are free to rotate on the shaft. The
pinion gear is fitted in a bore in the differential case
and is positioned at a right angle to the axle shafts.
OPERATION
In operation, power flow occurs as follows:
²The pinion gear rotates the ring gear
²The ring gear (bolted to the differential case)
rotates the case
²The differential pinion gears (mounted on the
pinion mate shaft in the case) rotate the side gears
²The side gears (splined to the axle shafts) rotate
the shafts
During straight-ahead driving, the differential pin-
ion gears do not rotate on the pinion mate shaft. This
occurs because input torque applied to the gears is
divided and distributed equally between the two side
gears. As a result, the pinion gears revolve with the
pinion mate shaft but do not rotate around it (Fig.
38).When turning corners, the outside wheel must
travel a greater distance than the inside wheel to
complete a turn. The difference must be compensated
for to prevent the tires from scuffing and skidding
through turns. To accomplish this, the differential
allows the axle shafts to turn at unequal speeds (Fig.
39). In this instance, the input torque applied to the
pinion gears is not divided equally. The pinion gears
now rotate around the pinion mate shaft in opposite
directions. This allows the side gear and axle shaft
attached to the outside wheel to rotate at a faster
speed.
Fig. 37 BOC Input Shaft
1 - GROOVED AREA (2 LOCATIONS)
2 - ROLLER MATING SURFACE
Fig. 38 Differential OperationÐStraight Ahead
Driving
1 - IN STRAIGHT AHEAD DRIVING EACH WHEEL ROTATES AT
100% OF CASE SPEED
2 - PINION GEAR
3 - SIDE GEAR
4 - PINION GEARS ROTATE WITH CASE
Fig. 39 Differential OperationÐOn Turns
1 - PINION GEARS ROTATE ON PINION SHAFT
RSREAR DRIVELINE MODULE3-43
BI-DIRECTIONAL OVERRUNNING CLUTCH (Continued)
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FLUID - DIFFERENTIAL
ASSEMBLY
STANDARD PROCEDURE - DIFFERENTIAL
ASSEMBLY FLUID CHANGE
The drain plug (Fig. 40) for the differential assem-
bly is located in the bottom of the differential assem-
bly case, toward the rear of the unit.
The fill plug (Fig. 41) for the differential assembly
is located on the rear of the assembly case.The correct fill level is to the bottom of the fill plug
hole. Be sure the vehicle is on a level surface, or is
hoisted in a level manner, in order to obtain the cor-
rect fill level.
(1) Raise the vehicle on a hoist.
(2) Position a drain pan under the differential
drain plug (Fig. 40).
(3) Remove the drain plug and allow the fluid to
drain into the pan.
(4) Install the drain plug and torque to 35 N´m (26
ft. lbs.).
(5) Re-position the drain pan under the differential
fill plug.
(6) Remove the differential fill plug (Fig. 41).
(7) Using a suction gun (Fig. 42) or equivalent, fill
the differential assembly with 0.7 L (1.48 pts.) of
MopartGear and Axle Lubricant (80W-90).
(8) Install the fill plug and torque to 35 N´m (26 ft.
lbs.).
FLUID
STANDARD PROCEDURE - OVERRUNNING
CLUTCH HOUSING FLUID CHANGE
(1) Raise vehicle on hoist.
(2) Position a drain pan under overrunning clutch
housing drain plug.
Fig. 40 Differential Drain Plug
1 - DIFFERENTIAL DRAIN PLUG
Fig. 41 Differential Fill Plug
1 - DIFFERENTIAL FILL PLUG
Fig. 42 Filling Differential
1 - DIFFERENTIAL ASSEMBLY
2 - SUCTION GUN
3 - 44 REAR DRIVELINE MODULERS
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