Chrysler Pacifica. Manual - part 446
OUTPUT SEAL
REMOVAL
(1) Raise vehicle on hoist.
(2) Remove rear driveline module. (Refer to 3 -
DIFFERENTIAL & DRIVELINE/REAR DRIVELINE
MODULE - REMOVAL)
(3) Use suitable screwdriver to remove output seal
(Fig. 69).
INSTALLATION
(1) Install output flange seal to differential hous-
ing using tool C4171A and 8493 (Fig. 70).
(2) Install rear driveline module. (Refer to 3 - DIF-
FERENTIAL
&
DRIVELINE/REAR
DRIVELINE
MODULE - INSTALLATION)
(3) Check differential assembly fluid level and
adjust as required. (Refer to 3 - DIFFERENTIAL &
DRIVELINE/REAR DRIVELINE MODULE/FLUID -
STANDARD PROCEDURE)
VISCOUS COUPLER
DESCRIPTION
The heart of the all-wheel drive system is the
inter-axle viscous coupling and bi-directional over-
running clutch. Under normal driving the vehicle
retains predominantly front wheel drive characteris-
tics. The all-wheel drive takes effect when the front
wheels start to slip. Under normal level road,
straight line driving, 100% of the torque is allocated
to the front wheels. The viscous coupler allows more
torque to the rear wheels in accordance with the
amount of slippage at the front wheels. The variable
torque distribution is automatic with no driver
inputs required.
OPERATION
The viscous coupler (Fig. 71) is a housing nearly
filled with a high viscosity silicone liquid and thin
metal plates alternately splined to an inner and
outer drum. The viscous coupler provides torque in
the following modes:
• Shear mode (normal operation)
• Hump mode (locked mode)
The inner plates are slotted around the radius and
the outer plates have holes in them. In the shear
mode (normal operation), the plates are evenly
spaced and the torque is created by the shearing of
the plates through the fluid and 90-100% of the
torque is applied to the rear axle. During the shear
mode, a fluid flow pattern is created from this design
(holes and slots). This fluid flow causes high pressure
on each side of each pair of plates and low pressure
between each pair of plates.
When a high speed difference (shear) occurs
because of loss of traction (one axle spinning faster
than the other), the silicone fluid expands as it heats
from this shearing. When the silicone expands to fill
the viscous coupler completely, this pressure differ-
ence is high enough to squeeze each pair of plates
together. The resulting hump torque is up to 8 times
higher than the shear torque. When the viscous cou-
pler is in the hump mode, it does not lock the axles
(undifferentiated 4-Wheel Drive). It controls the
amount of slippage while delivering maximum power
to the axle having greatest traction. Once the speed
difference equalizes the fluid and plates cool down
and the viscous coupler goes back to the shear mode.
Fig. 69 Axle Seal Removal
1 - SEAL
2 - SCREWDRIVER
Fig. 70 Axle Seal Installation
1 - TOOL C-4171
2 - TOOL 8493
CS
REAR DRIVELINE MODULE
3 - 53