2003 JEEP GRAND CHEROKEE no start

(8) Install anewcollapsible preload spacer on pin-
ion shaft and install pinion gear in the housing (Fig.
84).
(9) Install yoke with Installer C-3718 and Spanner
Wrench 6958 (Fig. 85).
(10) Install the yoke washer and a new nut on the
pinion gear and tighten the pinion nut until there is
zero bearing end-play.
(11) Tighten the nut to 271 N´m (200 ft. lbs.).
CAUTION: Never loosen pinion gear nut to decrease
pinion rotating torque and never exceed specified
preload torque. If preload torque or rotating torque
is exceeded a new collapsible spacer must be
installed.
(12) Using Spanner Wrench 6958 and a torque
wrench set at 474 N´m (350 ft. lbs.), (Fig. 86) slowly
tighten the nut in 6.8 N´m (5 ft. lbs.) increments
until the rotating torque is achieved. Measure the
rotating torque frequently to avoid over crushing the
collapsible spacer (Fig. 87).
NOTE: If more than 474 N´m (350 ft. lbs.) torque is
required to crush the collapsible spacer, the spacer
is defective and must be replaced.(13) Check bearing rotating torque with a inch
pound torque wrench (Fig. 87). The pinion gear rotat-
ing torque should be:
²Original Bearings: 1 to 2.25 N´m (10 to 20 in.
lbs.).
²New Bearings: 1.7 to 3.9 N´m (15 to 35 in. lbs.).
(14) Invert the differential case and start two ring
gear bolts. This will provide case-to-ring gear bolt
hole alignment.
Fig. 84 COLLAPSIBLE SPACER
1 - COLLAPSIBLE SPACER
2 - SHOULDER
3 - PINION GEAR
4 - DEPTH SHIM
5 - REAR BEARING
Fig. 85 PINION YOKE INSTALLER
1 - INSTALLER
2 - PINION YOKE
Fig. 86 PINION NUT
1 - SPANNER WRENCH
2 - PIPE
3 - TORQUE WRENCH
3 - 88 REAR AXLE - 198RBIWJ
PINION GEAR/RING GEAR (Continued)

and therefore creates pressure in the pump. The tun-
ing of the front and rear axle orifices and valves
inside the gerotor pump is unique and each system
includes a torque-limiting pressure relief valve to
protect the clutch pack, which also facilitates vehicle
control under extreme side-to-side traction varia-
tions. The resulting pressure is applied to the clutch
pack and the transfer of torque is completed.
Under conditions in which opposite wheels are on
surfaces with widely different friction characteristics,
Vari-loktdelivers far more torque to the wheel on
the higher traction surface than do conventional
Trac-loktsystems. Because conventional Trac-lokt
differentials are initially pre-loaded to assure torque
transfer, normal driving (where inner and outer
wheel speeds differ during cornering, etc.) produces
torque transfer during even slight side-to-side speed
variations. Since these devices rely on friction from
this preload to transfer torque, normal use tends to
cause wear that reduces the ability of the differential
to transfer torque over time. By design, the Vari-lokt
system is less subject to wear, remaining more con-
sistent over time in its ability to transfer torque. The
coupling assembly is serviced as a unit. From a ser-
vice standpoint the coupling also benefits from using
the same lubricant supply as the ring and pinion
gears.
DIAGNOSIS AND TESTING
GEAR NOISE
Axle gear noise can be caused by insufficient lubri-
cant, incorrect backlash, tooth contact, worn/damaged
gears, or the carrier housing not having the proper
offset and squareness.
Gear noise usually happens at a specific speed
range. The noise can also occur during a specific type
of driving condition. These conditions are accelera-
tion, deceleration, coast, or constant load.
When road testing, first warm-up the axle fluid by
driving the vehicle at least 5 miles and then acceler-
ate the vehicle to the speed range where the noise is
the greatest. Shift out-of-gear and coast through the
peak-noise range. If the noise stops or changes
greatly:
²Check for insufficient lubricant.
²Incorrect ring gear backlash.
²Gear damage.
Differential side gears and pinions can be checked
by turning the vehicle. They usually do not cause
noise during straight-ahead driving when the gears
are unloaded. The side gears are loaded during vehi-
cle turns. A worn pinion mate shaft can also cause a
snapping or a knocking noise.
BEARING NOISE
The axle shaft, differential and pinion bearings can
all produce noise when worn or damaged. Bearing
noise can be either a whining, or a growling sound.
Pinion bearings have a constant-pitch noise. This
noise changes only with vehicle speed. Pinion bearing
noise will be higher pitched because it rotates at a
faster rate. Drive the vehicle and load the differen-
tial. If bearing noise occurs, the rear pinion bearing
is the source of the noise. If the bearing noise is
heard during a coast, the front pinion bearing is the
source.
Worn or damaged differential bearings usually pro-
duce a low pitch noise. Differential bearing noise is
similar to pinion bearing noise. The pitch of differen-
tial bearing noise is also constant and varies only
with vehicle speed.
Axle shaft bearings produce noise and vibration
when worn or damaged. The noise generally changes
when the bearings are loaded. Road test the vehicle.
Turn the vehicle sharply to the left and to the right.
This will load the bearings and change the noise
level. Where axle bearing damage is slight, the noise
is usually not noticeable at speeds above 30 mph.
LOW SPEED KNOCK
Low speed knock is generally caused by a worn
U-joint or by worn side±gear thrust washers. A worn
pinion shaft bore will also cause low speed knock.
VIBRATION
Vibration at the rear of the vehicle is usually
caused by a:
²Damaged drive shaft.
²Missing drive shaft balance weight(s).
²Worn or out-of-balance wheels.
²Loose wheel lug nuts.
²Worn U-joint(s).
²Loose/broken springs.
²Damaged axle shaft bearing(s).
²Loose pinion gear nut.
²Excessive pinion yoke run out.
²Bent axle shaft(s).
Check for loose or damaged front-end components
or engine/transmission mounts. These components
can contribute to what appears to be a rearend vibra-
tion. Do not overlook engine accessories, brackets
and drive belts.
All driveline components should be examined
before starting any repair.
(Refer to 22 - TIRES/WHEELS - DIAGNOSIS AND
TESTING)
3 - 92 REAR AXLE - 226RBAWJ
REAR AXLE - 226RBA (Continued)

(13) Check bearing rotating torque with a inch
pound torque wrench (Fig. 87). The pinion gear rotat-
ing torque should be:
²
Original Bearings: 1 to 2.25 N´m (10 to 20 in. lbs.).
²New Bearings: 2.8 to 4 N´m (25 to 35 in. lbs.).
(14) Invert the differential case and start two ring
gear bolts. This will provide case-to-ring gear bolt
hole alignment.
(15) Invert the differential case in the vise.
(16) Installnewring gear bolts and alternately
tighten to 129-142 N´m (95-105 ft. lbs.) (Fig. 88).
CAUTION: Never reuse the ring gear bolts. The
bolts can fracture causing extensive damage.
NOTE: If equipped with Veri-LokTdifferential install
oil feed plenum and side bearing.
(17) Install differential in housing.
CAUTION: When installing a Vari-lokTdifferential
(Fig. 89), the oil feed tube must point to the bottom
of the housing. If differential is installed with the oil
feed tube pointed toward the top, the anti-rotation
tabs will be damaged.
(18)
Verify differential bearing preload, gear mesh
and contact pattern. Refer to Ajustments for procedure.
(19) Install differential cover and fill with gear
lubricant.(20) Install the propeller shaft with the reference
marks aligned.
(21) Remove supports and lower vehicle.
Fig. 87 PINION ROTATING TORQUE
1 - PINION YOKE/COMPANION FLANGE
2 - INCH POUND TORQUE WRENCH
Fig. 88 RING GEAR
1 - TORQUE WRENCH
2 - RING GEAR BOLT
3 - RING GEAR
4 - CASE
Fig. 89 VARI-LOK
1 - ANTI-ROTATION TAB
2 - OIL FEED TUBE
WJREAR AXLE - 226RBA 3 - 129
PINION GEAR/RING GEAR (Continued)

NOTE: The front outer brake shoes are equipped
with a wear indicator. The indicator will produce an
audible noise when it contacts the rotor surface.
BRAKE CHATTER
Brake chatter is usually caused by loose or worn
components, or glazed/burnt lining. Rotors with hard
spots can also contribute to chatter. Additional causes
of chatter are out-of-tolerance rotors, brake lining not
securely attached to the shoes, loose wheel bearings
and contaminated brake lining.
THUMP/CLUNK NOISE
Thumping or clunk noises during braking are fre-
quentlynotcaused by brake components. In many
cases, such noises are caused by loose or damaged
steering, suspension, or engine components.
STANDARD PROCEDURE
STANDARD PROCEDURE - MANUAL BLEEDING
Use Mopar brake fluid, or an equivalent quality
fluid meeting SAE J1703-F and DOT 3 standards
only. Use fresh, clean fluid from a sealed container at
all times.
Do not pump the brake pedal at any time while
bleeding. Air in the system will be compressed into
small bubbles that are distributed throughout the
hydraulic system. This will make additional bleeding
operations necessary.
Do not allow the master cylinder to run out of fluid
during bleed operations. An empty cylinder will allow
additional air to be drawn into the system. Check the
cylinder fluid level frequently and add fluid as
needed.
Bleed only one brake component at a time in the
following sequence:
(1) Fill the master cylinder reservoir with brake
fluid.
(2) If calipers are overhauled, open all caliper
bleed screws. Then close each bleed screw as fluid
starts to drip from it. Top off master cylinder reser-
voir once more before proceeding.
(3) Attach one end of bleed hose to bleed screw
and insert opposite end in glass container partially
filled with brake fluid (Fig. 1). Be sure end of bleed
hose is immersed in fluid.
(4) Open up bleeder, then have a helper press
down the brake pedal. Once the pedal is down close
the bleeder. Repeat bleeding until fluid stream is
clear and free of bubbles. Then move to the next
wheel.
STANDARD PROCEDURE - PRESSURE
BLEEDING
Use Mopar brake fluid, or an equivalent quality
fluid meeting SAE J1703-F and DOT 3 standards
only. Use fresh, clean fluid from a sealed container at
all times.
Do not pump the brake pedal at any time while
bleeding. Air in the system will be compressed into
small bubbles that are distributed throughout the
hydraulic system. This will make additional bleeding
operations necessary.
Do not allow the master cylinder to run out of fluid
during bleed operations. An empty cylinder will allow
additional air to be drawn into the system. Check the
cylinder fluid level frequently and add fluid as
needed.
Bleed only one brake component at a time in the
following sequence:
Follow the manufacturers instructions carefully
when using pressure equipment. Do not exceed the
tank manufacturers pressure recommendations. Gen-
erally, a tank pressure of 51-67 kPa (15-20 psi) is suf-
ficient for bleeding.
Fill the bleeder tank with recommended fluid and
purge air from the tank lines before bleeding.
Do not pressure bleed without a proper master cyl-
inder adapter. The wrong adapter can lead to leak-
age, or drawing air back into the system. Use
adapter provided with the equipment or Adapter
6921.
Fig. 1 Bleed Hose Setup
1 - BLEED HOSE
2 - FLUID CONTAINER PARTIALLY FILLED WITH FLUID
WJBRAKES - BASE 5 - 5
BRAKES - BASE (Continued)

SPECIAL TOOLS
BASE BRAKESBRAKE FLUID LEVEL SWITCH
REMOVAL
(1) Remove the wire connector from the fluid level
sensor.
(2) From the same side of the master cylinder res-
ervoir release the sensor locking taps with a small
screw driver.
(3) Pull the sensor out of the reservoir from the
connector side of the sensor.
INSTALLATION
(1) Install the sensor with a new o-ring into the
reservoir until the locking tabs are engaged.
(2) Install the wire connector to the fluid level sen-
sor.
RED BRAKE WARN INDICATOR
SWITCH
DESCRIPTION
A red warning lamp is used for the service brake
portion of the hydraulic system. The lamp is located
in the instrument cluster.
OPERATION
The lamp is turned on momentarily when the igni-
tion switch is turn to the on position. This is a self
test to verify the lamp is operational.
The red warning light alerts the driver if the fluid
level is low or the parking brakes are applied. A red
warning lamp with an amber warning lamp may
indicate a electronic brake distribution fault.
DIAGNOSIS AND TESTING - RED BRAKE
WARNING LAMP
The red warning lamp illuminates when the park-
ing brake is applied or when the fluid level in the
master cylinder is low. It will also illuminate at start
up as part of a bulb check.
If the light comes on, first verify that the parking
brakes are fully released. Then check pedal action
and fluid level. If a problem is confirmed, inspect the
brake hydraulic system for leaks.
A red warning lamp with a amber warning lamp
may indicate a electronic brake distribution fault.
Installer Caliper Dust Boot 8280
Handle C-4171
Adapter Pressure Bleeder 6921
WJBRAKES - BASE 5 - 7
BRAKES - BASE (Continued)

STANDARD PROCEDURE
STANDARD PROCEDURE - DOUBLE INVERTED
FLARING
A preformed metal brake tube is recommended and
preferred for all repairs. However, double-wall steel
tube can be used for emergency repair when factory
replacement parts are not readily available.
Special bending tools are needed to avoid kinking
or twisting of metal brake tubes. Special flaring tools
are needed to make a double inverted flare or ISO
flare.
(1) Cut off damaged tube with Tubing Cutter.
(2) Ream cut edges of tubing to ensure proper
flare.
(3) Install replacement tube nut on the tube.
(4) Insert tube in flaring tool.
(5) Place gauge form over the end of the tube.
(6) Push tubing through flaring tool jaws until
tube contacts recessed notch in gauge that matches
tube diameter.
(7) Tighten the tool bar on the tube
(8) Insert plug on gauge in the tube. Then swing
compression disc over gauge and center tapered flar-
ing screw in recess of compression disc (Fig. 4).
(9) Tighten tool handle until plug gauge is
squarely seated on jaws of flaring tool. This will start
the inverted flare.
(10) Remove the plug gauge and complete the
inverted flare.
STANDARD PROCEDURE - ISO FLARING
A preformed metal brake tube is recommended and
preferred for all repairs. However, double-wall steel
tube can be used for emergency repair when factory
replacement parts are not readily available.
Special bending tools are needed to avoid kinking
or twisting of metal brake tubes. Special flaring tools
are needed to make a double inverted flare or ISO
flare.
To make a ISO flare use Snap-OntFlaring Tool
TFM-428 or equivalent.
(1) Cut off damaged tube with Tubing Cutter.
(2) Remove any burrs from the inside of the tube.
(3) Install tube nut on the tube.
(4) Position the tube in the flaring tool flush with
the top of the tool bar (Fig. 5). Then tighten the tool
bar on the tube.
(5) Install the correct size adaptor on the flaring
tool yoke screw.
(6) Lubricate the adaptor.
(7) Align the adaptor and yoke screw over the tube
(Fig. 5).
(8) Turn the yoke screw in until the adaptor is
squarely seated on the tool bar.
Fig. 4 Inverted
Fig. 5 ISO Flaring
1 - ADAPTER
2 - LUBRICATE HERE
3 - PILOT
4 - FLUSH WITH BAR
5 - TUBING
6 - BAR ASSEMBLY
WJBRAKES - BASE 5 - 9
BRAKE LINES (Continued)

rates into layers, there is mineral oil or other fluid
contamination of the brake fluid.
If brake fluid is contaminated, drain and thor-
oughly flush system. Replace master cylinder with
reservoir, caliper seals, HCU and all hydraulic fluid
hoses.
SPECIFICATIONS
BRAKE FLUID
The brake fluid used in this vehicle must conform
to DOT 3 specifications and SAE J1703 standards.
No other type of brake fluid is recommended or
approved for usage in the vehicle brake system. Use
only Mopar brake fluid or an equivalent from a
tightly sealed container.
CAUTION: Never use reclaimed brake fluid or fluid
from an container which has been left open. An
open container of brake fluid will absorb moisture
from the air and contaminate the fluid.
CAUTION: Never use any type of a petroleum-based
fluid in the brake hydraulic system. Use of such
type fluids will result in seal damage of the vehicle
brake hydraulic system causing a failure of the
vehicle brake system. Petroleum based fluids would
be items such as engine oil, transmission fluid,
power steering fluid, etc.
FLUID RESERVOIR
REMOVAL
(1) Remove reservoir cap and remove fluid with a
cleansuction gun.
(2) Remove the wire connector from the brake fluid
level sensor.
(3) Insert the tool (Fig. 47) provided with the res-
ervoir to release the reservoir retaining tabs.
(4) Pull the reservoir straight up out of the cylin-
der.
(5) Remove and discard grommets from the cylin-
der body.
INSTALLATION
(1) Lubricate new grommets with clean brake
fluid. Install new grommets into the cylinder body.
CAUTION: Do not use tools to install the grommets.
Tools may cut, or tear the grommets. Install the
grommets using finger pressure only.(2) Start reservoir in grommets then press the res-
ervoir straight down to seat the reservoir into the
cylinder grommets.
CAUTION: Do not rock the reservoir during installa-
tion.
(3) Verify retaining tabs are seated.
(4) Install the wire connector to the brake fluid
level sensor.
(5) Fill master cylinder.
MASTER CYLINDER
DESCRIPTION
The master cylinder body is made of aluminum
and contains a primary and secondary piston assem-
bly. The cylinder body including the piston assem-
blies are not serviceable. If diagnosis indicates an
internal problem with the cylinder body, it must be
replaced as an assembly. The master cylinder has a
removable reservoir and fluid level indicator. The res-
ervoir, reservoir grommets, reservoir cap and fluid
level switch are the only replaceable parts on the
master cylinder.
Fig. 47 Release Tool
1 - RESERVOIR
2 - RELEASE TOOL
3 - RETAINING TABS
WJBRAKES - BASE 5 - 23
FLUID (Continued)

OPERATION
The master cylinder bore contains a primary and
secondary piston. The primary piston supplies
hydraulic pressure to the front brakes. The secondary
piston supplies hydraulic pressure to the rear brakes.
The master cylinder reservoir stores reserve brake
fluid for the hydraulic brake circuits.
DIAGNOSIS AND TESTING - MASTER
CYLINDER/POWER BOOSTER
NOTE: Inspect and repair any external fluid leaks
before performing test.
(1) Start engine and check booster vacuum hose
connections. A hissing noise indicates vacuum leak.
Correct any vacuum leak before proceeding.
(2)
Stop engine and shift transmission into Neutral.
(3) Pump brake pedal until all vacuum reserve in
booster is depleted.
(4) Press and hold brake pedal under light foot
pressure. The pedal should hold firm, if the pedal
falls away the master cylinder or HCU may be faulty
(internal leakage).
(5) Start engine and note pedal action. It should
fall away slightly under light foot pressure then hold
firm. If no pedal action is discernible, power booster,
vacuum supply, or vacuum check valve is faulty. Pro-
ceed to the POWER BOOSTER VACUUM TEST.
(6) If the POWER BOOSTER VACUUM TEST
passes, rebuild booster vacuum reserve as follows:
Release brake pedal. Increase engine speed to 1500
rpm, close the throttle and turn off the engine.
(7) Wait a minimum of 90 seconds and try brake
action again. Booster should provide two or more vac-
uum assisted pedal applications. If vacuum assist is
not provided, some component of the booster is faulty.
POWER BOOSTER VACUUM TEST
(1) Connect vacuum gauge to booster check valve
with short length of hose and T-fitting (Fig. 48).
(2) Start and run engine at curb idle speed for one
minute.
(3) Observe the vacuum supply. If vacuum supply
is not adequate, repair vacuum supply.
(4) Clamp hose shut between vacuum source and
check valve.
(5) Stop engine and observe vacuum gauge.
(6) If vacuum drops more than one inch HG (33
millibars) within 15 seconds, booster diaphragm,
check valve or check valve seal/grommet is faulty.
POWER BOOSTER CHECK VALVE TEST
(1) Disconnect vacuum hose from check valve.
(2)
Remove check valve and valve seal from booster.
(3) Use a hand operated vacuum pump for test.(4) Apply 51-67 kPa (15-20 in.) vacuum at large
end of check valve (Fig. 49).
(5) Vacuum should hold steady. If gauge on pump
indicates vacuum loss the check valve and seal
should be replaced.
Fig. 48 Typical Booster Vacuum Test Connections
1 - TEE FITTING
2 - SHORT CONNECTING HOSE
3 - CHECK VALVE
4 - CHECK VALVE HOSE
5 - CLAMP TOOL
6 - INTAKE MANIFOLD
7 - VACUUM GAUGE
Fig. 49 Vacuum Check Valve And Seal
1 - BOOSTER CHECK VALVE
2 - APPLY TEST VACUUM HERE
3 - VALVE SEAL
5 - 24 BRAKES - BASEWJ
MASTER CYLINDER (Continued)