2002 CHRYSLER TOWN AND COUNTRY Fuel

Light spark knock at low engine speeds is not
harmful to your engine. However, continued heavy
spark knock at high speeds can cause damage and
immediate service is required. Engine damage result-
ing from operation with a heavy spark knock may
not be covered by the new vehicle warranty.
Poor quality gasoline can cause problems such as
hard starting, stalling and hesitations. If you experi-
ence these symptoms, try another brand of gasoline
before considering service for the vehicle.
Over 40 auto manufacturers world-wide have
issued and endorsed consistent gasoline specifications
(the Worldwide Fuel Charter, WWFC) to define fuel
properties necessary to deliver enhanced emissions,
performance and durability for your vehicle. We rec-
ommend the use of gasolines that meet the WWFC
specifications if they are available.
REFORMULATED GASOLINE
Many areas of the country require the use of
cleaner burning gasoline referred to as ªreformulat-
edº gasoline. Reformulated gasoline contain oxygen-
ates, and are specifically blended to reduce vehicle
emissions and improve air quality.
We strongly support the use of reformulated gaso-
line. Properly blended reformulated gasoline will pro-
vide excellent performance and durability for the
engine and fuel system components.
GASOLINE/OXYGENATE BLENDS
Some fuel suppliers blend unleaded gasoline with
oxygenates such as 10% ethanol, MTBE, and ETBE.
Oxygenates are required in some areas of the country
during the winter months to reduce carbon monoxide
emissions. Fuels blended with these oxygenates may
be used in your vehicle.
CAUTION: DO NOT use gasoline containing METH-
ANOL. Gasoline containing methanol may damage
critical fuel system components.
MMT IN GASOLINE
MMT is a manganese-containing metallic additive
that is blended into some gasoline to increase octane.
Gasoline blended with MMT provide no performance
advantage beyond gasoline of the same octane num-
ber without MMT. Gasoline blended with MMT
reduce spark plug life and reduce emission system
performance in some vehicles. We recommend that
gasoline free of MMT be used in your vehicle. The
MMT content of gasoline may not be indicated on the
gasoline pump; therefore, you should ask your gaso-
line retailer whether or not his/her gasoline contains
MMT.
It is even more important to look for gasoline with-
out MMT in Canada because MMT can be used atlevels higher than allowed in the United States.
MMT is prohibited in Federal and California refor-
mulated gasoline.
SULFUR IN GASOLINE
If you live in the northeast United States, your
vehicle may have been designed to meet California
low emission standards with Cleaner-Burning Cali-
fornia reformulated gasoline with low sulfur. If such
fuels are not available in states adopting California
emission standards, your vehicles will operate satis-
factorily on fuels meeting federal specifications, but
emission control system performance may be
adversely affected. Gasoline sold outside of California
is permitted to have higher sulfur levels which may
affect the performance of the vehicle's catalytic con-
verter. This may cause the Malfunction Indicator
Lamp (MIL), Check Engine or Service Engine Soon
light to illuminate. We recommend that you try a dif-
ferent brand of unleaded gasoline having lower sulfur
to determine if the problem is fuel related prior to
returning your vehicle to an authorized dealer for
service.
CAUTION: If the Malfunction Indicator Lamp (MIL),
Check Engine or Service Engine Soon light is flash-
ing, immediate service is required; see on-board
diagnostics system section.
MATERIALS ADDED TO FUEL
All gasoline sold in the United States and Canada
are required to contain effective detergent additives.
Use of additional detergents or other additives is not
needed under normal conditions.
FUEL SYSTEM CAUTIONS
CAUTION: Follow these guidelines to maintain your
vehicle's performance:
²The use of leaded gas is prohibited by Federal
law. Using leaded gasoline can impair engine perfor-
mance, damage the emission control system, and
could result in loss of warranty coverage.
²An out-of-tune engine, or certain fuel or ignition
malfunctions, can cause the catalytic converter to
overheat. If you notice a pungent burning odor or
some light smoke, your engine may be out of tune or
malfunctioning and may require immediate service.
Contact your dealer for service assistance.
²When pulling a heavy load or driving a fully
loaded vehicle when the humidity is low and the tem-
perature is high, use a premium unleaded fuel to
help prevent spark knock. If spark knock persists,
lighten the load, or engine piston damage may result.
RSLUBRICATION & MAINTENANCE0-5
FLUID TYPES (Continued)
ProCarManuals.com

²The use of fuel additives which are now being
sold as octane enhancers is not recommended. Most
of these products contain high concentrations of
methanol. Fuel system damage or vehicle perfor-
mance problems resulting from the use of such fuels
or additives is not the responsibility of
DaimlerChrysler Corporation and may not be covered
under the new vehicle warranty.
NOTE: Intentional tampering with emissions control
systems can result in civil penalties being assessed
against you.
DESCRIPTION - FUEL REQUIREMENTS -
DIESEL ENGINE
WARNING: DO NOT USE ALCOHOL OR GASOLINE
AS A FUEL BLENDING AGENT. THEY CAN BE
UNSTABLE UNDER CERTAIN CONDITIONS AND
HAZARDOUS OR EXPLOSIVE WHEN MIXED WITH
DIESEL FUEL.
Use good quality diesel fuel from a reputable sup-
plier. For most year-round service, number 2 diesel
fuel meeting ASTM specification D-975 will provide
good performance. If the vehicle is exposed to
extreme cold (below -18ÉC/0ÉF) or is required to oper-
ate at colder than normal conditions for prolonged
periods, use climatize No. 2 diesel fuel or dilute the
No. 2 diesel fuel with 50% No. 1 diesel fuel. This will
provide better protection from fuel gelling or wax
plugging of the fuel filters.
Diesel fuel is seldom completely free of water. To
prevent fuel system trouble, including fuel line freez-
ing in winter, drain the accumulated water from the
fuel/water separator using the fuel/water separator
drain provided. If you buy good quality fuel and fol-
low the cold weather advice above, fuel conditioners
should not be required in your vehicle. If available in
your area, a high cetane ªpremiumº diesel fuel may
offer improved cold starting and warm up perfor-
mance.
DESCRIPTION - ENGINE OIL - DIESEL
ENGINES
Use only Diesel Engine Oil meeting standardMIL-
2104Cor API ClassificationCD or higherorCCML
D4, D5.
SAE VISCOSITY GRADE
CAUTION: Low viscosity oils must have the proper
API quality or the CCMC G5 designation.
To assure of properly formulated engine oils, it is
recommended that SAE Grade 10W-40 engine oilsthat meet Chrysler material standard MS-6395, be
used. European Grade 10W-40 oils are also accept-
able.
Oils of the SAE 5W-40 or 8W-80 grade number are
preferred when minimum temperatures consistently
fall below -12ÉC.
FLUID FILL/CHECK
LOCATIONS
DESCRIPTION
The fluid check/fill point locations are located in
each applicable service manual section.
LUBRICATION POINTS
DESCRIPTION
Lubrication point locations are located in each
applicable Sections.
MAINTENANCE SCHEDULES
DESCRIPTION
9Maintenance Schedule Information not included in
this section, is located in the appropriate Owner's
Manual.9
HOISTING
STANDARD PROCEDURE - HOISTING
Refer to Owner's Manual provided with vehicle for
proper emergency jacking procedures.
WARNING: THE HOISTING AND JACK LIFTING
POINTS PROVIDED ARE FOR A COMPLETE VEHI-
CLE. WHEN THE ENGINE OR REAR SUSPENSION
IS REMOVED FROM A VEHICLE, THE CENTER OF
GRAVITY IS ALTERED MAKING SOME HOISTING
CONDITIONS UNSTABLE. PROPERLY SUPPORT OR
SECURE VEHICLE TO HOISTING DEVICE WHEN
THESE CONDITIONS EXIST.
CAUTION: Do not position hoisting device on any
suspension component, including the front suspen-
sion crossmember, the rear leaf springs, and the
rear axle. Do not hoist on the front and rear
bumpers, the lower liftgate crossmember, the lower
radiator crossmember, the down standing flanges
on the sill or the front engine mount.
FOR PROPER HOIST PLACEMENT REFER
TO (Fig. 5).
0 - 6 LUBRICATION & MAINTENANCERS
FLUID TYPES (Continued)
ProCarManuals.com

The hoisting points are identified by S.A.E.
inverted triangle hoisting symbols (Fig. 5). The front
hoisting points are at the bottom of the font rail
below the hoisting symbol approximately 250 mm
behind the front suspension crossmember. When
using outboard lift hoists, verify that the hoist lift
pads have been properly adjusted to eliminate con-
tact between the hoist arm and the down standing
flange on the sill. The rear hoisting points are the
leaf spring front mounting brackets. The hoist pad
must be positioned to pick up the flanges on the
bracket, not the leaf spring.
When servicing the leaf springs or the leaf spring
mounting brackets, special provisions are required to
support the rear of the vehicle. Position the rear
hoist pads under the horizontal surface on the bot-
tom of the sill, inboard adjacent to the flange and
centered fore/aft between the jacking indicator tabs
on the lower flange.DO NOT HOIST ON THE
FLANGE.Place a soft pad between the hoist and the
painted surface on the sill to avoid scratching the fin-
ish.JUMP STARTING
STANDARD PROCEDURE - JUMP STARTING
WARNING: REVIEW ALL SAFETY PRECAUTIONS
AND WARNINGS. (Refer to 8 - ELECTRICAL/BAT-
TERY SYSTEM/BATTERY - STANDARD PROCE-
DURE).
WARNING: DO NOT JUMP START A FROZEN BAT-
TERY, PERSONAL INJURY CAN RESULT.
WARNING: DO NOT JUMP START WHEN MAINTE-
NANCE FREE BATTERY INDICATOR DOT IS BRIGHT
COLOR.
WARNING: DO NOT ALLOW JUMPER CABLE
CLAMPS TO TOUCH EACH OTHER WHEN CON-
NECTED TO A BOOSTER SOURCE.
WARNING: DO NOT USE OPEN FLAME NEAR BAT-
TERY
WARNING: REMOVE METALLIC JEWELRY WORN
ON HANDS OR WRISTS TO AVOID INJURY BY
ACCIDENTAL ARCING OF BATTERY CURRENT.
WARNING: WHEN USING A HIGH OUTPUT BOOST-
ING DEVICE, DO NOT ALLOW BATTERY VOLTAGE
TO EXCEED 16 VOLTS.
WARNING: REFER TO INSTRUCTIONS PROVIDED
WITH DEVICE BEING USED.
CAUTION: DO NOT ATTEMPT TO PUSH OR TOW
THE VEHICLE TO START IT. THE VEHICLE CANNOT
BE STARTED THIS WAY. PUSHING WITH ANOTHER
VEHICLE MAY DAMAGE THE TRANSAXLE OR THE
REAR OF THE VEHICLE.
(1) Raise hood on disabled vehicle and visually
inspect engine compartment for:
²Battery cable clamp condition, clean if necessary.
²Frozen battery.
²Clear or bright color test indicator, if equipped.
²Generator drive belt condition and tension.
²Fuel fumes or leakage, correct if necessary.
CAUTION: If the cause of starting problem on dis-
abled vehicle is severe, damage to booster vehicle
charging system can result.
Fig. 5 HOISTING AND JACKING POINTS
1- DRIVE ON LIFT
2 - FRAME CONTACT LIFT (SINGLE POST)
2 - CHASSIS LIFT (NON-AXLE DUAL POST)
2 - OUTBOARD LIFT (DUAL POST)
2 - FLOOR JACK
3 - S.A.E. HOISTING SYMBOLS
RSLUBRICATION & MAINTENANCE0-7
HOISTING (Continued)
ProCarManuals.com

(2) When using another vehicle as a booster
source, park the booster vehicle within cable reach.
Turn off all accessories, set the parking brake, place
the automatic transmission in PARK or the manual
transmission in NEUTRAL and turn the ignition
OFF.
(3) On disabled vehicle, place gear selector in park
or neutral and set park brake. Turn off all accesso-
ries.
(4) Connect jumper cables to booster battery. RED
clamp to positive terminal (+). BLACK clamp to neg-
ative terminal (-). DO NOT allow clamps at opposite
end of cables to touch, electrical arc will result.
Review all warnings in this procedure.
(5) On disabled vehicle, connect RED jumper cable
clamp to positive (+) terminal. Connect BLACK
jumper cable clamp to engine ground as close to the
ground cable attaching point as possible (Fig. 6).
(Refer to 8 - ELECTRICAL/BATTERY SYSTEM/BAT-
TERY - STANDARD PROCEDURE).
(6) Start the engine in the vehicle which has the
booster battery, let the engine idle a few minutes,
then start the engine in the vehicle with the dis-
charged battery.
CAUTION: Do not crank starter motor on disabled
vehicle for more than 15 seconds, starter may over-
heat and could fail.
(7) If engine does not start within 15 seconds, stop
cranking engine and allow starter to cool (15 min-
utes), before cranking again.DISCONNECT CABLE CLAMPS AS FOLLOWS:
²Disconnect BLACK cable clamp from engine
ground on disabled vehicle.
²When using a Booster vehicle, disconnect
BLACK cable clamp from battery negative terminal.
Disconnect RED cable clamp from battery positive
terminal.
²Disconnect RED cable clamp from battery posi-
tive terminal on disabled vehicle.
TOWING
STANDARD PROCEDURE - TOWING
WARNINGS AND CAUTIONS
WARNING: DO NOT ALLOW TOWING ATTACHMENT
DEVICES TO CONTACT THE FUEL TANK OR LINES,
FUEL LEAK CAN RESULT.
DO NOT LIFT OR TOW VEHICLE BY FRONT OR
REAR BUMPER.
DO NOT GO UNDER A LIFTED VEHICLE IF NOT
SUPPORTED PROPERLY ON SAFETY STANDS.
DO NOT ALLOW PASSENGERS TO RIDE IN A
TOWED VEHICLE.
USE A SAFETY CHAIN THAT IS INDEPENDENT
FROM THE TOWING ATTACHMENT DEVICE.
CAUTION: Do not damage brake lines, exhaust sys-
tem, shock absorbers, sway bars, or any other
under vehicle components when attaching towing
device to vehicle.
Do not secure vehicle to towing device by the use
of front or rear suspension or steering components.
Remove or secure loose or protruding objects from
a damaged vehicle before towing.
Refer to state and local rules and regulations before
towing a vehicle.
Do not allow weight of towed vehicle to bear on
lower fascia, air dams, or spoilers.
RECOMMENDED TOWING EQUIPMENT
To avoid damage to bumper fascia and air dams
use:
²FWD vehicles, use of a flat bed towing device or
a wheel lift is recommended (Fig. 7).
²AWD vehicles, a flat bed towing device or a
wheel lift and towing dolly is recommended (Fig. 7).
When using a wheel lift towing device, be sure the
disabled vehicle has at least 100 mm (4 in.) ground
clearance. If minimum ground clearance cannot be
reached, use a towing dolly. If a flat bed device is
used, the approach angle should not exceed 15
degrees.
Fig. 6 JUMPER CABLE CLAMP CONNECTIONS
1 - BATTERY NEGATIVE TERMINAL
2 - POSITIVE JUMPER CABLE
3 - TEST INDICATOR (IF EQUIPPED)
4 - BATTERY POSITIVE TERMINAL
5 - BATTERY
6 - NEGATIVE JUMPER CABLE
0 - 8 LUBRICATION & MAINTENANCERS
JUMP STARTING (Continued)
ProCarManuals.com

CONDITION POSSIBLE CAUSES CORRECTION
3. Incorrect front wheel camber 3. Check and reset front wheel camber
4. Power steering gear imbalance 4. Replace power steering gear
5. Wheel braking 5. Correct braking condition causing lateral
pull
Excessive Steering Free
Play1. Incorrect Steering Gear Adjustment 1. Adjust Or Replace Steering Gear
2. Worn or loose tie rod ends 2. Replace or tighten tie rod ends
3. Loose steering gear mounting bolts 3. Tighten steering gear bolts to specified
torque
4. Loose or worn steering shaft
coupler4. Replace steering shaft coupler
Excessive Steering Effort 1. Low tire pressure 1. Inflate all tires to recommended
pressure
2. Lack of lubricant in steering gear 2. Replace steering gear
3. Low power steering fluid level 3. Fill power steering fluid reservoir to
correct level
4. Loose power steering pump drive
belt4. Correctly adjust power steering pump
drive belt
5. Lack of lubricant in ball joints 5. Lubricate or replace ball joints
6. Steering gear malfunction 6. Replace steering gear
7. Lack of lubricant in steering coupler 7. Replace steering coupler
STANDARD PROCEDURE
STANDARD PROCEDURE - WHEEL ALIGNMENT
PRE-WHEEL ALIGNMENT INSPECTION
Before any attempt is made to change or correct
the wheel alignment, the following inspection and
necessary corrections must be made to ensure proper
alignment.
(1) Verify that the fuel tank is full of fuel. If the
tank is not full, the reduction in weight will affect
the curb height of the vehicle and the alignment
angles.
(2) The passenger and luggage compartments of
the vehicle should be free of any load that is not fac-
tory equipment.
(3) Check the tires on the vehicle. All tires must be
the same size and in good condition with approxi-
mately the same amount of tread wear. Inflate all
the tires to the recommended air pressure.
(4) Check the front wheel and tire assemblies for
excessive radial runout.
(5) Inspect lower ball joints and all steering link-
age for looseness, binding, wear or damage. Repair as
necessary.(6) Check suspension fasteners for proper torque
and retighten as necessary.
(7) Inspect all suspension component rubber bush-
ings for signs of wear or deterioration. Replace any
faulty bushings or components before aligning the
vehicle.
(8) Check the vehicle's curb height to verify it is
within specifications. Refer to Curb Height Measure-
ment.
WHEEL ALIGNMENT SETUP
(1) Position the vehicle on an alignment rack.
(2) Install all required alignment equipment on
the vehicle per the alignment equipment manufactur-
er's instructions. On this vehicle, a four-wheel align-
ment is recommended.
NOTE: Prior to reading the vehicle's alignment
readouts, the front and rear of vehicle should be
jounced. Induce jounce (rear first, then front) by
grasping the center of the bumper and jouncing
each end of vehicle an equal number of times. The
bumper should always be released when vehicle is
at the bottom of the jounce cycle.
(3) Read the vehicle's current front and rear align-
ment settings. Compare the vehicle's current align-
RSWHEEL ALIGNMENT2-51
WHEEL ALIGNMENT (Continued)
ProCarManuals.com

CAUTION: Do not twist front inner tie rod to steer-
ing gear rubber boots during front wheel Toe
adjustment.
(2) Loosen front inner to outer tie rod end jam
nuts (Fig. 12). Grasp inner tie rods at serrations and
rotate inner tie rods of steering gear (Fig. 12) to set
front toe to the preferred toe specification. (Refer to 2
- SUSPENSION/WHEEL ALIGNMENT - SPECIFI-
CATIONS)
(3) Tighten tie rod jam nuts (Fig. 12) to 75 N´m
(55 ft. lbs.) torque.
(4) Adjust steering gear to tie rod boots at the
inner tie rod.
(5) Remove steering wheel clamp.
(6) Remove the alignment equipment.
(7) Road test the vehicle to verify the steering
wheel is straight and the vehicle does not wander or
pull.
STANDARD PROCEDURE - CURB HEIGHT
MEASUREMENT
The wheel alignment is to be checked and all align-
ment adjustments made with the vehicle at its
required curb height specification.
Vehicle height is to be checked with the vehicle on
a flat, level surface, preferably a vehicle alignmentrack. The tires are to be inflated to the recommended
pressure. All tires are to be the same size as stan-
dard equipment. Vehicle height is checked with the
fuel tank full of fuel, and no passenger or luggage
compartment load.
Vehicle height is not adjustable. If the measure-
ment is not within specifications, inspect the vehicle
for bent or weak suspension components. Compare
the parts tag on the suspect coil spring(s) to the
parts book and the vehicle sales code, checking for a
match. Once removed from the vehicle, compare the
coil spring height to a correct new or known good coil
spring. The heights should vary if the suspect spring
is weak.
(1) Measure from the inboard edge of the wheel
opening fender lip directly above the wheel center
(spindle), to the floor or alignment rack surface.
(2) When measuring, the maximum left-to-right
differential is not to exceed 12.5 mm (0.5 in.).
(3) Compare the measurements to the specifica-
tions listed in the following Curb Height Specifica-
tions charts.
Fig. 11 Camber Adjustment Cam Bolt
1 - STEERING KNUCKLE
2 - CLEVIS BRACKET CAM STOP AREAS
3 - LOWER ECCENTRIC CAMBER ADJUSTMENT BOLT
Fig. 12 Front Wheel Toe Adjustment
1 - INNER TIE ROD SERRATION
2 - OUTER TIE ROD JAM NUT
3 - OUTER TIE ROD END
4 - INNER TIE ROD
5 - STEERING KNUCKLE
2 - 54 WHEEL ALIGNMENTRS
WHEEL ALIGNMENT (Continued)
ProCarManuals.com

CURB HEIGHT SPECIFICATIONS - LONG WHEEL BASE VEHICLES
TIRE SALES CODE/TIRE SIZE FRONT REAR
TM4 / 215/70 R 15754mm 10mm
29.68 in.   0.39 in.770mm 10mm
30.31 in.   0.39 in.
TM5 / 215/65 R 16755mm 10mm
29.72 in.   0.39 in.771mm 10mm
30.35 in.   0.39 in.
TTU / 215/60 R 17758mm 10mm
29.84 in.   0.39 in.774mm 10mm
30.47 in.   0.39 in.
CURB HEIGHT SPECIFICATIONS - SHORT WHEEL BASE VEHICLES
TIRE SALES CODE/TIRE SIZE FRONT REAR
TM4 / 215/70 R 15755mm 10mm
29.72 in.   0.39 in.770mm 10mm
30.31 in.   0.39 in.
TM5 / 215/65 R 16756mm 10mm
29.76 in.   0.39 in.771mm 10mm
30.35 in.   0.39 in.
STANDARD PROCEDURE - CURB HEIGHT
MEASUREMENT (EXPORT)
The wheel alignment is to be checked and all align-
ment adjustments made with the vehicle at its
required curb height specification.
Vehicle height is to be checked with the vehicle on
a flat, level surface, preferably a vehicle alignment
rack. The tires are to be inflated to the recommended
pressure. All tires are to be the same size as stan-
dard equipment. Vehicle height is checked with the
fuel tank full of fuel, and no passenger or luggage
compartment load.
Vehicle height is not adjustable. If the measure-
ment is not within specifications, inspect the vehicle
for bent or weak suspension components. Comparethe parts tag on the suspect coil spring(s) to the
parts book and the vehicle sales code, checking for a
match. Once removed from the vehicle, compare the
coil spring height to a correct new or known good coil
spring. The heights should vary if the suspect spring
is weak.
(1) Measure from the inboard edge of the wheel
opening fender lip directly above the wheel center
(spindle), to the floor or alignment rack surface.
(2) When measuring, the maximum left-to-right
differential is not to exceed 12.5 mm (0.5 in.).
(3) Compare the measurements to the specifica-
tions listed in the following Curb Height Specifica-
tions charts.
CURB HEIGHT SPECIFICATIONS - LONG WHEEL BASE VEHICLES WITH SDF SUSPENSION
TIRE SALES CODE/TIRE SIZE FRONT REAR
TMM / 215/65 R 16756mm 10mm
29.76 in.   0.39 in.772mm 10mm
30.39 in.   0.39 in.
CURB HEIGHT SPECIFICATIONS - LONG WHEEL BASE VEHICLES WITH SDF + SER
SUSPENSION
TIRE SALES CODE/TIRE SIZE FRONT REAR
TMM / 215/65 R 16756mm 10mm
29.76 in.   0.39 in.771mm 10mm
30.35 in.   0.39 in.
CURB HEIGHT SPECIFICATIONS - SHORT WHEEL BASE VEHICLES
TIRE SALES CODE/TIRE SIZE FRONT REAR
TMM / 215/65 R 16755mm 10mm
29.72 in.   0.39 in.770mm 10mm
30.31 in.   0.39 in.
RSWHEEL ALIGNMENT2-55
WHEEL ALIGNMENT (Continued)
ProCarManuals.com

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
ProCarManuals.com