2003 CHRYSLER CARAVAN lock

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.
Fig. 29 BOC Operation at Low Speeds With No
Front Wheel Slip
1 - CAGE
2 - ROLLER
3 - INPUT SHAFT
3 - 36 REAR DRIVELINE MODULERS
BI-DIRECTIONAL OVERRUNNING CLUTCH (Continued)
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STEADY STATE, HIGH SPEED, NO WHEEL SLIP
The roller cage positions the rollers on the input
shaft flats during low and high speed overrunning
and during initial BOC lockup. The roller cage is
rotating at input shaft (propeller shaft) speed at all
times. At low speeds, the friction shoes (Fig. 31) are
pressed against the friction ground via the garter
spring (Fig. 32), creating a drag force on the roller
cage. The drag force positions the cage, which in turn
positions the rollers to one side of the flat. The direc-
tion of this drag force (position of the roller) is depen-
dent on the input (propeller shaft) rotational
direction. Since the rollers are always in contact with
the outer race, due to centrifugal forces, the rollers
want to follow the outer race due to drag. During
overrunning operation, the outer race is rotating
faster than the input; causing the rollers to want to
traverse the flat from one side to the other. During
low speeds, the brake shoes counteract this effect. To
avoid excessive wear, the ground shoes are designed
to lift off from the friction ground due to centrifugal
forces at higher rotational speeds.
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 crossesthe 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.
Fig. 30 BOC Operation with Front Wheel SlipFig. 31 Front View of BOC
1 - GARTER SPRING
2 - FRICTION BRAKE SHOES
3 - FRICTION GROUND CONNECTED TO GROUND TAB
4 - INPUT SHAFT
Fig. 32 Location of the Grounding Element
1 - DIFFERENTIAL HOUSING
2 - GROUND TAB
3 - GARTER SPRING
RSREAR DRIVELINE MODULE3-37
BI-DIRECTIONAL OVERRUNNING CLUTCH (Continued)
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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). The
high 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)
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
Fig. 34 BOC Operation During High Speed Lock-up Without High Speed Latch
3 - 38 REAR DRIVELINE MODULERS
BI-DIRECTIONAL OVERRUNNING CLUTCH (Continued)
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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. 46) 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:²Shear mode (normal operation)
²Hump 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. 45 Filling Overrunning Clutch Case
1 - OVERRUNNING CLUTCH HOUSING FILL HOLE
2 - SUCTION GUN
3 - 42 REAR DRIVELINE MODULERS
VISCOUS COUPLER (Continued)
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Fig. 46 Bi-directional Overrunning Clutch (BOC) and Viscous Coupler Powerflow
1 - POWERFLOW - BOC OVERUNNING 6 - VISCOUS COUPLER
2 - POWERFLOW - BOC LOCKED 7 - BOC ROLLER CAGE
3 - BOC GROUND TAB 8 - BOC INPUT SHAFT
4 - FRICTION BRAKE SHOES 9 - INPUT FLANGE
5 - BOC ROLLERS
RSREAR DRIVELINE MODULE3-43
VISCOUS COUPLER (Continued)
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INSTALLATION
(1) Using tool 8802, install input flange seal to
overrunning clutch case (Fig. 51).
(2) Install input flange (Fig. 52).
(3) Install flange nut and washer. Using tool 6958,
torque flange nut to 135 N´m (100 ft. lbs.) (Fig. 53).
(4) Install propeller shaft. (Refer to 3 - DIFFER-
ENTIAL & DRIVELINE/PROPELLER SHAFT -
INSTALLATION)
(5) Lower vehicle.
OUTPUT FLANGE SEAL
REMOVAL
(1) Raise vehicle on hoist.
(2) Remove rear halfshaft inner joint at differen-
tial output flange (Fig. 54).
(3) Using two screwdrivers and wood blocks to pro-
tect differential housing casting, pry output flange
out of differential (Fig. 55).
(4) Use suitable screwdriver to remove output
flange seal (Fig. 56).
Fig. 50 Input Flange Seal Removal
1 - INPUT FLANGE SEAL
2 - SCREWDRIVER
Fig. 51 Input Flange Seal Installation
1 - TOOL 8802
2 - HAMMER
Fig. 52 Input Flange
1 - INPUT FLANGE/SHIELD
Fig. 53 Input Flange Nut
1 - INPUT FLANGE
2 - TOOL 6958
RSREAR DRIVELINE MODULE3-45
INPUT FLANGE SEAL (Continued)
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INSTALLATION
(1) Install output flange seal to differential hous-
ing using tool C4171A and 8493 (Fig. 57).
Fig. 54 Inner Half Shaft Bolts
1 - SHAFT
2 - FLANGE
Fig. 55 Output Flange Removal
1 - WOOD BLOCK
2 - PRYBAR
3 - OUTPUT SHAFT
4 - PRYBAR
5 - WOOD BLOCK
6 - DIFFERENTIAL CASE
Fig. 56 Output Flange Seal Removal
1 - OUTPUT FLANGE SEAL
2 - SCREWDRIVER
Fig. 57 Output Flange Seal Installation
1 - DRIVER HANDLE C4171
2 - INSTALLER 8493
3 - 46 REAR DRIVELINE MODULERS
OUTPUT FLANGE SEAL (Continued)
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CLEANING - CALIPER...................25
INSPECTION - CALIPER..................25
ASSEMBLY
ASSEMBLY - CALIPER GUIDE PIN
BUSHINGS (DISC/DISC BRAKES).........25
ASSEMBLY - CALIPER PISTON AND SEAL . . 26
INSTALLATION
INSTALLATION - FRONT DISC BRAKE
CALIPER (DISC/DISC BRAKES)...........27
INSTALLATION - FRONT DISC BRAKE
CALIPER (DISC/DRUM BRAKES)..........27
DISC BRAKE CALIPER - REAR
REMOVAL - REAR DISC BRAKE CALIPER....27
DISASSEMBLY - CALIPER PISTON AND SEAL . 28
CLEANING - CALIPER...................29
INSPECTION - CALIPER..................29
ASSEMBLY - CALIPER PISTON AND SEAL . . . 29
INSTALLATION - REAR DISC BRAKE CALIPER . 30
DISC BRAKE CALIPER ADAPTER
REMOVAL - FRONT DISC BRAKE CALIPER
ADAPTER...........................31
INSTALLATION - FRONT DISC BRAKE
CALIPER ADAPTER....................31
DISC BRAKE CALIPER GUIDE PINS
REMOVAL - DISC BRAKE CALIPER GUIDE
PINS (DISC/DRUM BRAKES).............31
INSTALLATION - DISC BRAKE CALIPER
GUIDE PINS (DISC/DRUM BRAKES).......31
DRUM
REMOVAL.............................32
INSTALLATION.........................32
FLUID
DIAGNOSIS AND TESTING - BRAKE FLUID
CONTAMINATION.....................32
STANDARD PROCEDURE - BRAKE FLUID
LEVEL CHECKING.....................32
SPECIFICATIONS
BRAKE FLUID........................33
JUNCTION BLOCK
DESCRIPTION - NON-ABS JUNCTION BLOCK . 33
OPERATION - NON-ABS JUNCTION BLOCK . . 33
REMOVAL - NON-ABS JUNCTION BLOCK....33
INSTALLATION - NON-ABS JUNCTION BLOCK . 33
MASTER CYLINDER
DESCRIPTION
DESCRIPTION........................34
DESCRIPTION - RHD..................35
OPERATION...........................35
STANDARD PROCEDURE - MASTER
CYLINDER BLEEDING..................35
REMOVAL
REMOVAL - LHD......................36
REMOVAL - RHD......................37
DISASSEMBLY - MASTER CYLINDER (FLUID
RESERVOIR).........................37
ASSEMBLY - MASTER CYLINDER (FLUID
RESERVOIR).........................38INSTALLATION
INSTALLATION - LHD..................38
INSTALLATION - RHD..................39
PEDAL TORQUE SHAFT - RHD
REMOVAL.............................39
INSTALLATION.........................39
POWER BRAKE BOOSTER
DESCRIPTION.........................40
OPERATION...........................41
DIAGNOSIS AND TESTING - POWER BRAKE
BOOSTER...........................41
REMOVAL
REMOVAL - LHD......................42
REMOVAL - RHD......................43
INSTALLATION
INSTALLATION - LHD..................46
INSTALLATION - RHD..................47
PROPORTIONING VALVE
DESCRIPTION - PROPORTIONING VALVE
(HEIGHT SENSING)....................48
OPERATION - PROPORTIONING VALVE
(HEIGHT SENSING)....................48
DIAGNOSIS AND TESTING -
PROPORTIONING VALVE (HEIGHT
SENSING)...........................49
REMOVAL - PROPORTIONING VALVE
(HEIGHT SENSING)....................50
INSTALLATION - PROPORTIONING VALVE
(HEIGHT SENSING)....................51
ROTOR
DIAGNOSIS AND TESTING - BRAKE ROTOR . . 51
STANDARD PROCEDURE - BRAKE ROTOR
MACHINING..........................53
REMOVAL - FRONT BRAKE ROTOR........54
INSTALLATION - FRONT BRAKE ROTOR.....54
SPECIFICATIONS
BRAKE ROTOR.......................55
BRAKE ROTOR - EXPORT..............55
SUPPORT PLATE - DRUM BRAKE
REMOVAL.............................56
INSTALLATION.........................56
WHEEL CYLINDERS
REMOVAL.............................57
INSPECTION..........................57
INSTALLATION.........................57
PARKING BRAKE
DESCRIPTION
DESCRIPTION........................57
DESCRIPTION - EXPORT...............58
OPERATION...........................58
STANDARD PROCEDURE
STANDARD PROCEDURE - PARKING
BRAKE AUTOMATIC ADJUSTER TENSION
RELEASE...........................58
STANDARD PROCEDURE - PARKING
BRAKE AUTOMATIC ADJUSTER TENSION
RESET.............................59
5 - 2 BRAKES - BASERS
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