front JEEP CHEROKEE 1994 Service Manual PDF

0.015 in. (0.38 mm) thick shim on this hub. This will
provide the required differential bearing preload
torque.
(10) Install bearings on hubs with Installer
C-3716-A and Handle C-4171 (Fig. 59).
(11) Match each bearing cup with bearing (origi-
nal). Install the cups on the bearings.
DIFFERENTIAL INSTALLATION
(1) Position Spreader W-129-B with the tool dowel
pins seated in the locating holes (Fig. 60). Install the
holddown clamps and tighten the tool turnbuckle fin-
ger-tight.
(2) Install a pilot stud at the left side of the differ-
ential housing. Attach Dial Indicator to housing pilotstud. Load the indicator plunger against the opposite
side of the housing (Fig. 60) and zero the indicator.
CAUTION: Do not spread over 0.38 mm (0.015 in). If
the housing is over-separated, it could be distorted
or damaged.
(3) Spread the housing enough to install the case
in the housing. Measure the distance with the dial
indicator (Fig. 60).
(4) Remove the dial indicator.
(5) Install case in the housing. Tap the differential
case to ensure the bearings are fully seated (Fig. 61).
Remove the spreader.
(6) Install the bearing caps at their original loca-
tions (Fig. 62). Tighten the bearing cap bolts to 61
Nzm (45 ft. lbs.) torque.
Fig. 59 Differential Bearing Installation
Fig. 60 Spread Differential Housing
Fig. 61 Differential Installation
Fig. 62 Differential Bearing Cap Reference Letters
JFRONT SUSPENSION AND AXLE 2 - 43

BACKLASH AND CONTACT PATTERN ANALYSIS
(1) Rotate assembly several revolutions to seat
bearings. Measure backlash at three equally spaced
locations around the perimeter of the ring gear with
a dial indicator (Fig. 63).
The ring gear backlash must be within 0.005 -
0.008 inch (0.12 - 0.20 mm). It cannot vary more
than 0.002 inch (0.05 mm) between the points
checked.
If backlash must be adjusted, transfer shims from
one side of carrier to the other side. Adjust the back-
lash accordingly (Fig. 64).DO NOT INCREASE
THE TOTAL SHIM PACK THICKNESS, EXCES-
SIVE BEARING PRELOAD AND DAMAGE
WILL OCCUR.If the mesh and backlash steps have been followed
in the procedures above, good gear teeth contact pat-
terns should exist.
The ring gear teeth contact patterns will show if
the pinion gear depth is correct. It will also show if
the ring gear backlash has been adjusted correctly.
The backlash must be maintained within the speci-
fied limits until the correct tooth contact patterns are
obtained.
(2) Apply a thin coat of hydrated ferric oxide (yel-
low oxide of iron) to the drive and coast side of the
ring gear teeth.
(3) Rotate the ring gear one complete revolution in
both directions while a load is being applied. Insert a
pry bar between the differential housing and the case
flange. This action will produce distinct contact pat-
terns on both the drive side and coast side of the ring
gear teeth.
(4) Note patterns in compound. Refer to (Fig. 65)
for interpretation of contact patterns and adjust ac-
cordingly.
FINAL ASSEMBLY
(1) Install the axle shafts. Refer to Axle Shaft In-
stallation in this Group.
(2) Scrape the residual sealant from the housing
and cover mating surfaces. Clean the mating sur-
faces with mineral spirits. Apply a bead of MOPARt
Silicone Rubber Sealant on the housing cover (Fig.
66). Allow the sealant to cure for a few minutes.
Install the housing cover within 5 minutes af-
ter applying the sealant. If not installed the seal-
ant must be removed and another bead applied.
(3) Install the cover on the differential with the at-
taching bolts. Install the identification tag. Tighten
the cover bolts with 41 Nzm (30 ft. lbs.) torque.
CAUTION: Overfilling the differential can result in
the lubricant foaming and overheating.
(4) Refill the differential housing with the speci-
fied quantity of MOPARtHypoid Gear Lubricant.
(5) Install the fill hole plug and tighten to 34 Nzm
(25 ft. lbs.) torque.Fig. 63 Ring Gear Backlash Measurement
Fig. 64 Backlash Shim Adjustment
2 - 44 FRONT SUSPENSION AND AXLEJ

Fig. 65 Gear Tooth Contact Patterns
JFRONT SUSPENSION AND AXLE 2 - 45

AXLE SPECIFICATIONS
Fig. 66 Typical Housing Cover With Sealant
MODEL 30 FRONT AXLE
2 - 46 FRONT SUSPENSION AND AXLEJ

TORQUE SPECIFICATIONS
XJ FRONT SUSPENSION COMPONENTS
YJ FRONT SUSPENSION COMPONENTS
MODEL 30 AXLE
JFRONT SUSPENSION AND AXLE 2 - 47

BRAKES
CONTENTS
page page
ABS BRAKE DIAGNOSIS.................. 3
ABS COMPONENT SERVICE.............. 47
ABS SYSTEM OPERATION............... 39
ANTILOCK BRAKE SYSTEM OPERATION.... 43
BRAKE BLEEDINGÐBRAKE FLUID AND
LEVELÐBRAKELINES AND HOSES....... 13
BRAKE PEDAL AND BRAKELIGHT SWITCH . . 65
DISC BRAKES.......................... 24DRUM BRAKES........................ 34
GENERAL INFORMATION.................. 1
PARKING BRAKES...................... 56
POWER BRAKE BOOSTER................ 22
SERVICE BRAKE DIAGNOSIS.............. 7
SPECIFICATIONS....................... 67
STANDARD MASTER CYLINDER........... 20
GENERAL INFORMATION
INDEX
page page
Antilock Brake System (ABS)................ 1
Brake Fluid/Lubricants/Cleaning Solvents........ 1
Brake Safety Precautions................... 2
Brake Warning Lights...................... 1
Brakelining Material........................ 1Hydraulic Components..................... 1
Jeep Body Code Letters.................... 2
Power Brakes............................ 1
Wheel Brake Components................... 1
WHEEL BRAKE COMPONENTS
Front disc and rear drum brakes are used on all
models. The disc brake components consist of single
piston calipers and ventilated rotors. The rear drum
brakes are dual shoe, units with cast brake drums.
The parking brake mechanism is lever and cable
operated. The cables are attached to actuating levers
mounted on the rear drum brake secondary shoes.
The parking brake mechanism is operated by a foot
pedal on YJ models and a hand lever on XJ models.
POWER BRAKES
Power brakes are standard on all models. A vac-
uum operated power booster is used for standard and
ABS brake applications.
HYDRAULIC COMPONENTS
A dual reservoir master cylinder is used for all
standard brake applications. A combination propor-
tioning valve/pressure differential switch is used. A
center feed style master cylinder is used for ABS
brake applications.
BRAKELINING MATERIAL
The factory installed brakelining on all models con-
sists of an organic base material combined with me-
tallic particles. The lining does not contain asbestos.
BRAKE WARNING LIGHTS
A red, brake warning light is used to alert the
driver if a pressure differential exists between the
front and rear hydraulic systems. The light also
alerts the driver when the parking brakes are ap-
plied. The light illuminates for a few seconds at start
up as part of a bulb check procedure.
An additional warning light is used on models with
antilock brakes. This light is amber in color and is
located in the same side of the instrument cluster as
the red warning light. The amber light illuminates
only when an ABS system fault occurs.
ANTILOCK BRAKE SYSTEM (ABS)
An antilock brake system (ABS) is available on
XJ/YJ models. The system is an electronically oper-
ated, all-wheel brake control system. The ABS sys-
tem is designed to retard wheel lockup during
periods of high wheel slip braking. Refer to the anti-
lock brake section for operation and service informa-
tion.
BRAKE FLUID/LUBRICANTS/CLEANING SOLVENTS
Recommended fluid for all Jeep vehicles is Mopar
DOT 3 brake fluid, or an equivalent meeting SAE
J1703 and DOT 3 standards.
JBRAKES 5 - 1

ABS BRAKE DIAGNOSIS
INDEX
page page
ABS Fault Diagnosis....................... 4
ABS System Wiring and Electrical Circuits...... 4
ABS Warning Light Display.................. 3
Brake Warning Light Display................. 4
Diagnosis Procedures...................... 3
ECU Diagnosis........................... 4
HCU Diagnosis........................... 4Loss of Sensor Input....................... 3
Operating Sound Levels.................... 3
Rear Speed Sensor Air Gap................. 3
Steering Response........................ 3
Vehicle Response in Antilock Mode............ 3
Wheel/Tire Size and Input Signals............. 3
DIAGNOSIS PROCEDURES
ABS diagnosis involves three basic steps. First is
observation of the warning light display. Second is a
visual examination for low fluid level, leaks, parking
brakes applied, or obvious damage to system compo-
nents or wires. The third step involves using the
DRB II scan tool to identify a faulty component.
The visual examination requires a check of reser-
voir fluid level and all system components. Things to
look for are leaks, loose connections, or obvious com-
ponent damage.
The final diagnosis step involves using the DRB II
scan tool to determine the specific circuit or compo-
nent at fault. The tester is connected to the ABS di-
agnostic connector in the passenger compartment.
The connector is at the driver side of the center con-
sole under the instrument panel. Refer to the DRB II
scan tool Manual for tester procedures. Also refer to
the ABS Fault Diagnosis charts at the end of this
section for additional diagnosis information.
Initial faults should be cleared and the vehicle road
tested to reset any faults that remain in the system.
Faults can be cleared with the DRB II scan tool.
REAR SPEED SENSOR AIR GAP
The front wheel sensors are fixed and cannot be ad-
justed. Only the rear sensor air gap is adjustable. Air
gap must be set with a brass feeler gauge.
Correct air gap is important to proper signal gen-
eration. An air gap that is too large may cause com-
plete loss of sensor input. Or, a gap that is too small
could produce a false input signal, or damaging con-
tact between the sensor and tone ring.
WHEEL/TIRE SIZE AND INPUT SIGNALS
Antilock system operation is dependant on accurate
signals from the wheel speed sensors. Ideally, the ve-
hicle wheels and tires should all be the same size
and type. However, the Jeep ABS system is designed
to function with a compact spare tire installed.
OPERATING SOUND LEVELS
The ABS pump and solenoid valves may produce
some sound as they cycle on and off. This is a normal
condition and should not be mistaken for faulty oper-
ation.
VEHICLE RESPONSE IN ANTILOCK MODE
During antilock braking, the HCU solenoid valves
cycle rapidly in response to ECU inputs.
The driver will experience a pulsing sensation
within the vehicle as the solenoids decrease, hold, or
increase pressure as needed. A pulsing brake pedal
will also be noted.
The pulsing sensation occurs as the solenoids cycle
during antilock mode braking. A slight pulse in the
brake pedal may also be noted during the dynamic
self check part of system initialization.
STEERING RESPONSE
A modest amount of steering input is required dur-
ing extremely high deceleration braking, or when
braking on differing traction surfaces. An example of
differing traction surfaces would be when the left
side wheels are on ice and the right side wheels are
on dry pavement.
LOSS OF SENSOR INPUT
Sensor malfunctions will most likely be due to
loose connections, damaged sensor wires, incorrect
rear sensor air gap, or a malfunctioning sensor. Ad-
ditional causes of sensor faults would be sensor and
tone ring misalignment or damage.
ABS WARNING LIGHT DISPLAY
ABS Light Illuminates At Startup
The amber ABS light illuminates at startup as
part of the system self check feature. The light illu-
minates for 2-3 seconds then goes off as part of the
normal self check routine.
ABS Light Remains On After Startup
An ABS system fault is indicated when the light
remains on after startup. Diagnosis with the DRB II
JBRAKES 5 - 3

SERVICE BRAKE DIAGNOSIS
INDEX
page page
Component Inspection...................... 8
Diagnosing Parking Brake Problems.......... 10
Diagnosing Service Brake Problems........... 8
Diagnosis Procedures...................... 7
General Information........................ 7Master Cylinder/Power Booster Test.......... 11
Power Booster Check Valve Test............ 11
Power Booster Vacuum Test................ 12
Preliminary Brake Check.................... 7
Road Testing............................ 7
GENERAL INFORMATION
The diagnosis information in this section covers
service brake components which include:
²disc brake calipers
²disc brakeshoes
²drum brake wheel cylinders
²drum brakeshoes and brake drums
²drum brake support plates
²parking brake mechanism
²master cylinder/combination valve
²vacuum power brake booster
²brake pedal and brakelight switch
²brake warning light
DIAGNOSIS PROCEDURES
Service brake diagnosis involves determining if a
problem is related to a mechanical, hydraulic or vac-
uum operated component. A preliminary brake
check, followed by road testing and component in-
spection are needed to determine a problem cause.
Road testing will either verify proper brake opera-
tion or confirm the existence of a problem. Compo-
nent inspection will, in most cases, identify the
actual part responsible for a problem.
The first diagnosis step is the preliminary brake
check. This involves inspecting fluid level, parking
brake action, wheel and tire condition, checking for
obvious leaks or component damage and testing
brake pedal response. A road test will confirm or
deny the existence of a problem. The final diagnosis
procedure involves road test analysis and a visual in-
spection of brake components.
PRELIMINARY BRAKE CHECK
(1) If amber antilock light is illuminated, refer to
Antilock Brake System Diagnosis. However, if red
warning light is illuminated, or if neither warning
light is illuminated, continue with diagnosis.
(2) Check condition of tires and wheels. Damaged
wheels and worn, damaged, or underinflated tires
can cause pull, shudder, tramp and a condition simi-
lar to grab.
(3) If complaint was based on noise when braking,
check suspension components. Jounce front and rearof vehicle and listen for noise that might be caused
by loose, worn, or damaged suspension or steering
components.
(4) Inspect brake fluid level:
(a) If vehicle has one-piece master cylinder, fluid
level should be to 6 mm (1/4 in.) of reservoir rim. If
vehicle two-piece, removable reservoir, correct level
is to top of indicator rings in reservoir.
(b) On models with ABS brakes, preferred level
is to MAX mark on reservoir. Acceptable level is
between MAX and MIN marks.
(c) Remember that fluid level in the front and
rear reservoir compartments will decrease in pro-
portion to normal lining wear. However, if fluid
level is abnormally low, look for leaks at calipers,
wheel cylinders, brakelines and master cylinder.
(5) Inspect brake fluid condition:
(a) Fluid should be reasonably clear and free of
foreign material.Note that brake fluid tends to
darken over time. This is normal and should
not be mistaken for contamination. If fluid is
clear of foreign material, it is OK.
(b) If fluid is highly discolored, or appears to con-
tain foreign material, drain out a sample with a
clean suction gun. Pour sample in a glass container
and note condition.
(c) If fluid separates into layers, obviously con-
tains oil, or a substance other than brake fluid,
system seals and cups will have to be replaced and
hydraulic system flushed.
(6) Check parking brake operation. Verify free
movement and full release of cables and foot pedal or
hand lever. Also note if vehicle was being operated
with parking brake partially applied.
(7) Check brake pedal operation. Verify that pedal
does not bind and has adequate free play. If pedal
lacks free play, check pedal and power booster for be-
ing loose or for bind condition. Do not road test until
condition is corrected.
(8) If components inspected look OK, road test the
vehicle.
ROAD TESTING
(1) If amber warning light is illuminated, problem
is with antilock system component. Refer to Antilock
Brake System Diagnosis.
JBRAKES 5 - 7

(2) If red warning light is illuminated, or if neither
warning light is illuminated, make several stops and
note pedal action and brake response.
(3) Check brake pedal response with transmission
in Neutral and engine running. Pedal should remain
firm under steady foot pressure. If pedal falls away,
problem is either in vacuum booster or master cylin-
der.
(4) During road test, make normal and firm brake
stops in 25-40 mph range. Note faulty brake opera-
tion such as pull, grab, drag, noise, fade, pedal pul-
sation, etc.
(5) Inspect suspect brake components and refer to
problem diagnosis information for causes of various
brake conditions.
COMPONENT INSPECTION
Fluid leak points and dragging brake units can
usually be located without removing any compo-
nents. The area around a leak point will be wet with
fluid. The components at a dragging brake unit
(wheel, tire, rotor) will be quite warm or hot to the
touch.
Other brake problem conditions will require compo-
nent removal for proper inspection. Raise the vehicle
and remove the necessary wheels for better visual ac-
cess.
During component inspection, pay particular atten-
tion to heavily rusted/corroded brake components
(e.g. rotors, caliper pistons, brake return/holddown
springs, support plates, etc.).
Heavy accumulations of rust may be covering se-
vere damage to a brake component. It is wise to re-
move surface rust in order to accurately determine
the depth of rust penetration and damage. Light sur-
face rust is fairly normal and not a major concern (as
long as it is removed). However, heavy rust buildup,
especially on high mileage vehicles may cover struc-
tural damage to such important components as
brakelines, rotors, support plates, and brake boosters.
Refer to the wheel brake service procedures in this
group for more information.
DIAGNOSING SERVICE BRAKE PROBLEMS
BRAKE WARNING LIGHT OPERATION
The red brake warning light will illuminate under
the following conditions:
²for 2-3 seconds at startup as part of normal bulb
check
²parking brakes applied
²low pedal caused by malfunction in front/rear
brake hydraulic circuit (differential switch valve ac-
tuated)
If the red light remains on after startup, first ver-
ify that the parking brakes are fully released. Then
check pedal action and fluid level. A red light indi-
cates that the valve in the differential pressureswitch has been actuated. If a problem is confirmed,
inspect the hydraulic system and wheel brake compo-
nents.
On models with ABS brakes, the amber warning
light only illuminates when an ABS component has
malfunctioned. The ABS light operates indepen-
dently of the red warning light. Refer to the antilock
brake section for more detailed diagnosis informa-
tion.
PEDAL FALLS AWAY
A brake pedal that falls away under steady foot
pressure is generally the result of a system leak. The
leak point could be at a brakeline, fitting, hose,
wheel cylinder, or caliper. Internal leakage in the
master cylinder caused by worn or damaged piston
cups, may also be the problem cause.
If leakage is severe, fluid will be evident at or
around the leaking component. However internal
leakage in the master cylinder will not be physically
evident. Refer to the cylinder test procedure in this
section.
LOW PEDAL
If a low pedal is experienced, pump the pedal sev-
eral times. If the pedal comes back up, worn lining
and worn rotors or drums are the most likely causes.
However, if the pedal remains low and/or the warn-
ing light illuminates, the problem is in the master
cylinder, wheel cylinders, or calipers.
A decrease in master cylinder fluid level may only
be the result of normal lining wear. Fluid level will
decrease as lining wear occurs. It is a result of the
outward movement of caliper and wheel cylinder pis-
tons to compensate for normal wear.
SPONGY PEDAL
A spongy pedal is most often caused by air in the
system. However, thin drums or substandard brake
lines and hoses will also cause a condition similar to
a spongy pedal. The proper course of action is to
bleed the system, or replace thin drums and suspect
quality brake lines and hoses.
HARD PEDAL OR HIGH PEDAL EFFORT
A hard pedal or high pedal effort may be due to
lining that is water soaked, contaminated, glazed, or
badly worn. The power booster or check valve could
also be faulty. Test the booster and valve as de-
scribed in this section.
BRAKE DRAG
Brake drag occurs when the lining is in constant
contact with the rotor or drum. Drag can occur at
one wheel, all wheels, fronts only, or rears only. It is
a product of incomplete brakeshoe release. Drag can
be minor or severe enough to overheat the linings,
rotors and drums.
5 - 8 BRAKESJ

Brake drag also has a direct effect on fuel economy.
If undetected, minor brake drag can be misdiagnosed
as an engine or transmission/torque converter prob-
lem.
Minor drag will usually cause slight surface char-
ring of the lining. It can also generate hard spots in
rotors and drums from the overheat/cool down pro-
cess. In most cases, the rotors, drums, wheels and
tires are quite warm to the touch after the vehicle is
stopped.
Severe drag can char the brake lining all the way
through. It can also distort and score rotors and
drums to the point of replacement. The wheels, tires
and brake components will be extremely hot. In se-
vere cases, the lining may generate smoke as it chars
from overheating.
An additional cause of drag involves the use of in-
correct length caliper mounting bolts. Bolts that are
too long can cause a partial apply condition. The cor-
rect caliper bolts have a shank length of 67 mm
(2.637 in.), plus or minus 0.6 mm (0.0236 in.). Refer
to the Disc Brake service section for more detail on
caliper bolt dimensions and identification.
Some common causes of brake drag are:
²loose or damaged wheel bearing
²seized or sticking caliper or wheel cylinder piston
²caliper binding on bushings or slide surfaces
²wrong length caliper mounting bolts (too long)
²loose caliper mounting bracket
²distorted brake drum or shoes
²rear brakeshoes binding on worn/damaged support
plates
²severely rusted/corroded components
²misassembled components.
If brake drag occurs at all wheels, the problem may
be related to a blocked master cylinder compensator
port or faulty power booster (binds-does not release).
The brakelight switch can also be a cause of drag.
An improperly mounted or adjusted brakelight
switch can prevent full brake pedal return. The re-
sult will be the same as if the master cylinder com-
pensator ports are blocked. The brakes would be
partially applied causing drag.
BRAKE FADE
Brake fade is a product of overheating caused by
brake drag. However, overheating and subsequent
fade can also be caused by riding the brake pedal,
making repeated high deceleration stops in a short
time span, or constant braking on steep roads. Refer
to the Brake Drag information in this section for
causes.
PEDAL PULSATION
Pedal pulsation is caused by components that are
loose, or beyond tolerance limits.
Disc brake rotors with excessive lateral runout or
thickness variation, or out of round brake drums arethe primary causes of pulsation. Other causes are
loose wheel bearings or calipers and worn, damaged
tires.
PULL
A front pull condition could be the result of:
²contaminated lining in one caliper
²seized caliper piston
²binding caliper
²wrong caliper mounting bolts (too long)
²loose caliper
²loose or corroded mounting bolts
²improper brakeshoes
²damaged rotor
²incorrect wheel bearing adjustment (at one wheel)
A worn, damaged wheel bearing or suspension
component are further causes of pull. A damaged
front tire (bruised, ply separation) can also cause
pull. Wrong caliper bolts (too long) will cause a par-
tial apply condition and pull if only one caliper is in-
volved.
A common and frequently misdiagnosed pull condi-
tion is where direction of pull changes after a few
stops. The cause is a combination of brake drag fol-
lowed by fade at the dragging brake unit.
As the dragging brake overheats, efficiency is so
reduced that fade occurs. If the opposite brake unit is
still functioning normally, its braking effect is mag-
nified. This causes pull to switch direction in favor of
the brake unit that is functioning normally.
When diagnosing a change in pull condition, re-
member that pull will return to the original direction
if the dragging brake unit is allowed to cool down
(and is not seriously damaged).
REAR BRAKE GRAB
Rear grab (or pull) is usually caused by contami-
nated lining, bent or binding shoes and support
plates, or improperly assembled components. This is
particularly true when only one rear wheel is in-
volved. However, when both rear wheels are affected,
the master cylinder or proportioning valve could be
at fault.
BRAKES DO NOT HOLD AFTER DRIVING
THROUGH DEEP WATER PUDDLES
This condition is generally caused by water soaked
lining. If the lining is only wet, it can be dried by
driving with the brakes lightly applied for a mile or
two. However, if the lining is both wet and dirty, dis-
assembly and cleaning will be necessary.
BRAKE FLUID CONTAMINATION
There are two basic causes of brake fluid contami-
nation. The first involves allowing dirt, debris, or
other liquid materials to enter the cylinder reservoirs
JBRAKES 5 - 9