flat tire DODGE TRUCK 1993 Service Repair Manual

INTRODUCTION

INTRODUCTION

DESIGNATIONS,
LABELS/PLATES/DECALS,
CODES
AND DIMENSIONS/WEIGHTS .
CONTENTS

page
MEASUREMENT
AND TORQUE
... 1 SPECIFICATIONS
page

. 11

DESIGNATIONS, LABELS/PLATES/DECALS, CODES
AND
DIMENSIONS/WEIGHTS
INDEX

page

Engine
and
Transmission/Transfer
Case
Identification
2

Engine/Transmission/GVWR
4

Equipment
Identification
Plate
3
International
Vehicle Control
and
Display
Symbols
10

Major Component
Identification 3
VEHICLE DESIGNATIONS The Vehicle Code chart lists description and code
for Ram Truck and Sport Utility vehicles. The codes are used to identify vehicle types in charts, captions
and in service procedures. The vehicle codes are
dif­

ferent than the Vehicle Identification Number (VIN) or the wheelbase/model code.
VEHICLE SAFETY CERTIFICATION
LABEL
A certification label is attached to the left side
B-pillar. The label certifies that the vehicle conforms
to Federal Motor Vehicle Safety Standards (FMVSS).
The label also lists the: • Month and year of vehicle manufacture
• Gross Vehicle Weight Rating (GVWR). The gross
front and rear axle weight ratings (GAWR's) are
based on a minimum rim size and maximum cold tire inflation pressure Vehicle Identification Number (VIN)
Type of vehicle
Type of rear wheels (single or dual) Bar code
Month, Day and Hour (MDH) of final assembly
VEHICLE IDENTIFICATION NUMBER (VIN) PLATE The Vehicle Identification Number (VIN) plate is
attached to the top left side of the instrument panel.
The VIN contains 17 characters that provide data
concerning the vehicle. Refer to the decoding chart to
determine the identification of a vehicle.
page

Trailer
Towing Specifications
4

Vehicle Code Plate
2

Vehicle Designations
1

Vehicle Dimension
4

Vehicle
Identification
Number (VIN) Plate
1

Vehicle Safety
Certification
Label
............. 1

Vehicle Weights
4
VEHICLE CODE
DESIGNATIONS
VEHICLE CODE
= AD
(DODGE
RAM

PICKUP
&
CHASSIS
CAB)

VEHICLE
FAMILY LINE DESCRIPTION
AD1
D150

AD2
D250

AD3
D350
PICKUP

4x2

AD5
W150
AD6
W250

AD7
W350
PICKUP

4x4

AD2
D250
AD3
D350
CHASSIS
CAB

4x2

AD6
W250
AD7
W350
CHASSIS
CAB

4x4

AD4
AD100

AD4
AD150
SPORT
UTILITY
4x2

AD8
AD100

AD8 AD
150
SPORT
UTILITY
4x4
J90IN-32

0 - 2
LUBRICATION
AND
MAINTENANCE

• Commercial service
When a vehicle is continuously subjected to severe
driving conditions, lubricate:
• Body components
• All the driveline coupling joints
• Steering linkage More often than normal driving conditions

DUSTY
AREAS
With this type of severe driving condition, special
care should be given to the:
• Engine air cleaner filter
• PCV filter
• Crankcase ventilation system
• Brake booster control valve air filter. Verify that the filters and the associated compo­
nents are clean. Also verify that they are functioning
effectively. This will minimize the amount of abra­ sive particles that enter the engine.

OFF-ROAD
(4WD)
OPERATION
After off-road (4WD) operation, inspect the under­
side of the vehicle. Inspect the:
• Tires
• Body structure
• Steering components
• Suspension components • Exhaust system
• Threaded fasteners

HARSH
SURFACE ENVIRONMENTS
After extended operation in harsh environments,
the brake drums, brake linings, and rear wheel bear­ ings should be inspected and cleaned. This will pre­
vent wear and erratic brake action.

ROUTINE MAINTENANCE
The following routine maintenance is recommended
on a monthly basis: TIRES—Inspect the tires for unusual wear/damage.
Determine if the inflation pressure is adequate for
the vehicle load. BATTERY—Inspect and clean the terminals.
Tighten the terminals if necessary. FLUIDS—Determine if the component fluid levels
are acceptable. Add fluid, if necessary. LIGHTS/ELECTRICAL—Test all the electrical sys­
tems in the vehicle for proper operation. It is also recommended that the engine oil and the
washer fluid level be determined at each fuel fill-up.

VEHICLE
NOISE CONTROL
Vehicles with a GVWR of 4 535 kg (10,000 lbs), or
more, are required to comply with Federal Exterior Noise Regulations (Fig. 2).
VEHICLE
NOISE
EMISSION
CONTROL INFORMATION

DATE
OF
VEHICLE
MANUFACTURE

THIS
VEHICLE CONFORMS
TO
U.S. EPA REGULATIONS FOR NOISE EMISSION

APPLICABLE
TO
MEDIUM
AND HEAVY
DUTY
TRUCKS. THE
FOLLOWING
ACTS OR THE CAUSING THEREOF BY ANY PERSON ARE PROHIBITED BY THE NOISE CONTROL ACT
OF 1972. (A) THE
REMOVAL
OR

RENDERING
INOPERATIVE, OTHER
THAN
FOR
PURPOSES
OF
MAINTENANCE,
REPAIR.
OR REPLACEMENT, OF ANY NOISE CONTROL DEVICE OR ELEMENT OF
DESIGN
(LISTED
IN
THE
OWNERS
MANUAL)
INCORPORATED
INTO
THIS
VEHICLE
IN COMPLIANCE
WITH
THE NOISE CONTROL
ACT:
(B) THE
USE
OF
THIS
VEHICLE
AFTER SUCH DEVICE
OR
ELEMENT
OF
DESIGN HAS BEEN REMOVED
OR
RENDERED
INOPERATIVE.

PU626D

Fig.
2 Vehicle
Noise
Emission
Control Information
Label

UNAUTHORIZED
DEFEAT
OF
NOISE
CONTROL COMPONENTS
Federal law prohibits removal, altering or other­
wise defeating any noise control component. This in­
cludes before or after the vehicle is in use. Federal
law also prohibits the use of a vehicle after a noise
control component is defeated.

REQUIRED MAINTENANCE/SERVICE
FOR
NOISE
CONTROL

The following maintenance is required after each
6-month or 9 600 km (6,000 miles) interval. This will
ensure that the vehicle noise control components are
operating properly.

EXHAUST SYSTEM
Inspect exhaust system for exhaust leaks and dam­
aged components. The exhaust hangers, clamps and
U-bolts should be attached and in good condition.
Burned or ruptured mufflers, damaged exhaust pipes should be replaced. Refer to Group 11—Exhaust Sys­
tem/Intake Manifold for service information.

AIR
FILTER
HOUSING/CANISTER
Inspect the air filter assembly for proper fit. Verify
the cover is securely attached to the housing/canis­
ter. Inspect all the air filter housing hoses for con­ nections. The gasket between the air filter housing and throttle body must be in good condition. The air
filter element should be clean and serviced according
to the maintenance schedule.

FUEL
REQUIREMENTS
GASOLINE
ENGINES
All engines require the use of unleaded gasoline to
reduce the effects of lead to the environment. Also unleaded fuel is necessary to prevent damage to the
catalytic converter/02 sensor. The fuel must have a
minimum octane rating of 87 based on the (R + M)/2
calculation method.

LUBRICATION
AND
MAINTENANCE
0-11

J
DRIVE-ON
HOIST

I
FRAME
CONTACT
HOIST
TWIN
POST
CHASSIS
HOIST

FLOOR
JACK
RROOD30
Fig.
8 Correct Vehicle Lifting
Locations
An axle tube
A body side sill
A steering linkage component
A drive shaft
The engine or transmission oil pan
The fuel tank
• A front suspension arm Use the correct frame rail lifting locations only
(Fig. 8).
HOIST A vehicle can be lifted with:
• A single-post, frame-contact hoist
• A twin-post, chassis hoist
• A ramp-type, drive-on hoist
When a frame-contact type hoist is used, verify
that the lifting pads are positioned properly (Fig. 8).

WARNING:
WHEN
A
SERVICE
PROCEDURE
RE­
QUIRES
THE
REMOVAL
OF
THE
REAR
AXLE,
FUEL

TANK,
OR
SPARE
TIRE,
EITHER:

• PLACE ADDITIONAL WEIGHT ON THE REAR
END OF THE VEHICLE
« ATTACH THE VEHICLE TO THE HOIST
« PLACE JACK STANDS UNDER THE VEHICLE
FOR SUPPORT TO PREVENT TIPPING WHEN
THE CENTER OF BALANCE CHANGES
4WD VEHICLES A standard hoist can be used to lift a 4WD vehicle.
The hoist should be inspected for adequate clearance. The lift arms, pads or ramps should be adjusted to
ensure that there is adequate clearance (Fig. 9).
ADJUSTMENT
PAD

ii 7
MAINTAIN
CLEARANCE
HOIST
ARM

RK44

Fig.
9 Lifting 4WD Vehicle
With
Single-Post
Hoist—
Typical
When a twin-post hoist is used, a 4 x 4 x 12-inch
wood spacer also could be required. Place the wood spacer under the front axle (opposite the differential
housing). This will maintain balance and level lift­ ing.

CAUTION:
The
block
that
is
used must
be
secured in
a
safe manner. This
will
ensure
that
it
will
not un­

balance
the
vehicle.
VEHICLE
TOWING
RECOMMENDATIONS
When it is necessary to tow a Ram Truck, the rec­
ommended method is either:
• the sling-type, rear-end raised towing method; or
• the wheel-lift towing method with a tow dolly lo­
cated under the front wheels. A vehicle with flat-bed hauling equipment can also
be used to transport a disabled vehicle.

SLING-TYPE
FLAT
BED
RR0OD29
Fig.
10 Tow Vehicles
With
Approved
Equipment

0
- 32
LUBRICATION
AND
MAINTENANCE

•

Fig.
5 Parking Brake Ratio Lever Lubrication (2) Note any indication of brake overheating,
wheel dragging or the vehicle pulling to one side.
(3) Evaluate any performance complaints received
from the owner/operator. (4) Repair the brake system as necessary (refer to
Group 5—Brakes for additional information and ser­
vice procedures).

BODY
COMPONENT
MECHANISMS
LUBRICATION REQUIREMENTS
All operating mechanisms and linkages should be
lubricated when necessary. This will maintain ease of operation and provide protection against rust and
excessive wear. The door weatherstrip seals should
be lubricated to prolong their life as well as to im­ prove door sealing.

LUBRICANT SPECIFICATIONS
All applicable exterior and interior vehicle operat­
ing mechanisms should be:
• Inspected • Cleaned
• All the pivoting/sliding contact areas on the mech­ anisms should then be lubricated.
MOPAR®Multi-Mileage Lubricant or an equiva­
lent, should be used to lubricate the mechanisms.
The door weatherstrip seals should be lubricated
with silicone lubricant spray. Refer to the Body Lu­
bricant Specifications chart below for additional lu­
bricant applications.

LUBRICATION
(1) When necessary, lubricate the cab and cargo
box operating mechanisms with the specified lubri­
cants.

(2) Apply silicone lubricant to a cloth and wipe it
on door seals to avoid over-spray that can soil pas­
senger clothing. (3) Before applying lubricant, the component
should be wiped clean. After lubrication, any excess
lubricant should be removed.
(4) The hood latch, latch release mechanism, latch
striker and safety latch should be lubricated periodi­
cally.
(5) The door lock cylinders should be lubricated 2
times each year (preferably autumn and spring): • Spray a small amount of lock cylinder lubricant di­
rectly into the lock cylinder
• Apply a small amount to the key and insert it into
the lock cylinder • Rotate it to the locked position and then back to
the unlocked position several times
• Remove the key. Wipe the lubricant from it with a
clean cloth to avoid soiling of clothing.

TIRES
RECOMMENDED MAINTENANCE
The condition of the tires should be inspected. The
inflation pressures tested/corrected at the same time as the engine oil is changed and the oil filter is re­
placed.
The tires/wheels should be rotated periodically to
ensure even tread wear. The tires/wheels should be
rotated at the first 12 000 km (7,500-miles) interval.
Thereafter, at each 24 000 km (15,000-miles) inter­
val.
INSPECTION
Inspect the tires for excessive wear, damage. Test
the tires for the recommended inflation pressure and adjust the pressure accordingly. Refer to the tire in­
flation pressure decal located on the left door face. Also to Group 22—Tires And Wheels for tire pres­sure charts, tire replacement, and treadwear indica­

tors.

ROTATION
Tires/wheels should be rotated according to the rec­
ommended interval. The first tire/wheel rotation is
the most important for establishing the prevention of uneven tread wear. After rotation, adjust the tire in­
flation pressure to the air pressure recommended on
the decal located on the left door face.
Refer to Group 22—Tires And Wheels for the rec­
ommended method of tire/wheel rotation.

HEADLAMPS

MAINTENANCE SCHEDULE
Every six months check the headlamp beams to en­
sure that the headlamp beams are correctly posi­
tioned.

AIM
ADJUSTMENT
Refer to Group 8L—Lamps for headlamp aim ad­
justment procedures.

•

FRONT
SUSPENSION
AND
AXLE
2 - 5 (4) Front wheels for excessive radial, lateral
runout and unbalance. Refer to Group 22, Wheels and Tires for diagnosis information.
(5) Suspension components for wear and noise. Check
components for correct torque. Refer to Groups 2 and 3, Suspension and Axle for additional information.

WHEEL
ALIGNMENT
MEASUREMENTS/ADJUSTMENTS
The front wheel alignment positions must be set to
the specified limits. This will prevent abnormal tire
tread wear. The equipment manufacturer's recommenda­
tions for use of their
equipment
should always
be followed. All
damaged
front suspension sys­
tem components
should
be replaced. Do not at­ tempt to straighten any
bent
component.

CAMBER AND CASTER-2WD VEHICLES Camber and caster angle adjustments involve repo­
sitioning the upper suspension arm cam adjustment
bolts (Fig. 2). Alignment adjustments are accom­
plished by loosening the nuts and changing the posi­
tion of the cam bolt.
(1) Remove all foreign material from the adjust­
ment bolt threads.
(2) Record the camber and caster measurements
before loosening the adjustment bolt nuts.
(3) The camber angle should be adjusted as near as
possible to the preferred angle. The caster should be
the same at both sides of the vehicle. Refer to the Specifications chart.
CAMBER AND CASTER—4WD VEHICLES For 4WD vehicles, the correct wheel camber (verti­
cal tilt) angle is factory preset at zero degree (0°).
Camber cannot be altered by adjustment.
CAUTION: Do not attempt to
adjust
the
camber
an­
gle by
heating
or bending the axle or any
suspen­

sion
component. If camber angle is
incorrect,
the
component(s)
causing
an
incorrect
angle must be replaced.
(1) It is important that the camber (vertical tilt)
angle be the same for both front wheels.
(2) The camber angle should be measured with ac­
curate wheel alignment equipment. The acceptable
range is -1° to +1°. Refer to the Specifications chart.
Road test the vehicle and observe the steering
wheel return-to-center position. Before road testing,
check
and
correct
the tire
inflation pressures. Inflate
both
of the front tires
with exactly the
same
pressure.
During the road test, make vehicle turns to both
the left and right. If the steering wheel returns to­
ward the center position unassisted, the caster angle is correct. However, if the steering wheel does not re­ turn toward the center position unassisted, an incor­
rect caster angle is probable.
(1) The caster angle is factory preset at positive
two degrees
(
+
2°).
The acceptable range is +1/2° to +
3
1/2°.
(2) The caster angle should be measured with ac­
curate wheel alignment equipment.
(3) Caster angle can be adjusted by installing ta­
pered shims between the front axle pads and the spring brackets. The caster angle should be adjusted
as near as possible to the preferred angle.
(4) Record the caster measurement before remov­
ing the original shims from the spring pads.
(5) The caster should be the same at both sides of
the vehicle. Refer to the Specifications chart.
RN1030

Fig.
2 Caster &
Camber
Adjustment Location—2WD
Vehicles

WHEEL TOE POSITION The wheel toe position adjustment should be the fi­
nal front wheel alignment adjustment. In all in­ stances, follow the equipment manufacturer's
recommended procedure.
(1) Secure the steering wheel with the front wheels
in the straight-ahead position. For vehicles equipped
with power steering, start the engine before straight­ ening the wheels.
With power steering, the engine should be op­
erating during the wheel toe position adjust­
ment.
(2) Loosen the tie rod adjustment sleeve clamp
bolts (Fig. 3).
(3) Adjust the wheel toe position by rotating the
tie rod adjustment sleeve (Fig. 3). Rotate each tie-rod end in the direction of
sleeve rotation during the adjustment (Fig. 3).
This will ensure that both tie-rod ends are at the center of their travel.
(4) If applicable, turn the ignition switch off.

3
- 6
REAR SUSPENSION
AND
AXLE

•

NUT PIPE
SOCKET
WRENCH
(DRIVER)

FLAT
THREADED
WASHER
ROD
J8917-20

Fig.
6
Spring
Eye
Bushing
Removal
(3) Align
the
bushing with
the
spring
eye and

tighten
the nut
located
at the
socket wrench
end of

the threaded
rod.
Tighten until
the
bushing
is
forced into
the
spring
eye.

The bushing must
be
centered
in the
spring

eye.
The
ends
of the
bushing must
be
flush
or
slightly recessed within
the end
surfaces
of the

spring
eye.
8ERW1GE DIAGNOSIS
INDEX
page

Driveline
Snap
8

Gear
and
Bearing Noise
7

General
Information
6
Limited
Slip
Differential
8
page
Low Speed Knock
.........................
8
Rear
Axle
Alignment
.......................
7

Tire
Noise
7
Vibration
8

GENERAL INFORMATION
Axle bearing problem conditions
are
usually caused
by: • Insufficient
or
incorrect lubricant
• Foreign matter/water contamination
• Incorrect bearing preload torque adjustment When serviced,
the
bearings must
be
cleaned thor­
oughly. They should
be
dried with lint-free shop tow­

els.
Never
dry
bearings with compressed
air.

This will overheat them
and
brinell
the
bearing surfaces. This will result
in
noisy operation after
repair. Axle gear problem conditions
are
usually
the
result

of:

• Insufficient lubrication
• Incorrect
or
contaminated lubricant
• Overloading (excessive engine torque)
• Incorrect clearance
or
backlash adjustment Insufficient lubrication
is
usually
the
result
of a

housing cover leak.
It can
also
be
from worn axle shaft
or
pinion gear seals. Check
for
cracks
or
porous
areas
in the
housing
or
tubes.
Using
the
wrong lubricant will cause overheating
and gear failure. Gear tooth cracking
and
bearing
spalling
are
indicators
of
this.
Axle component breakage
is
most often
the
result

of:

• Severe overloading
• Insufficient lubricant
• Incorrect lubricant • Improperly tightened components
Common causes
of
overloading
is
from full-throttle
acceleration. Overloading occurs when towing
heavier than normal loads. Component breakage
can
occur when
the
wheels
are
spun excessively. Insuffi­
cient
or
incorrect lubricants contribute
to
breakage
through overheating. Loose differential components can also cause breakage. Incorrect bearing preload
or
gear backlash will
not

result
in
component breakage. Mis-adjustment will
produce enough noise
to
cause service repair before
a

•

RfAR SUSPENSION
AND
AXLE
3 - 7 failure occurs. If a mis-adjustment condition is not
corrected, component failure can result.

REAR
AXLE ALIGNMENT

MEASUREMENT The following procedure can be used to determine
if abnormal rear tire tread wear is the result of a
bent or deformed rear axle shaft.
(1) Raise both rear wheels off the surface with a
frame contact hoist. (2) Attach a one-inch long piece of masking tape at
the center of each tire tread for use as reference marks.
(3) Rotate the rear wheels until both reference
marks face the front of the vehicle. Measure the dis­
tance between the outside edges of the two pieces of
tape.
Record this measurement as the front of tire (FTR) measurement.
(4) Rotate the rear wheels until both reference
marks face the rear of the vehicle. Measure the dis­
tance between the outside edges of the two pieces of
tape.
Record this measurement as the rear of tire (RTR) measurement.
(5) Subtract the (RTR) measurement from the
(FTR) measurement to obtain the amount of wheel

toe.
The acceptable rear wheel toe-in position is 1/16 inch (1.6 mm) to 3/16 inch (4.8 mm) toe-out.
(6) Rotate the rear wheels until the reference
marks are facing downward. Measure the distance
between the outside edges of the two pieces of tape. Record this measurement as the bottom of tire (BTR)
measurement.
(7) Average the (FTR) and the (RTR) distance
measurements. Subtract the (BTR) measurement
from this average distance to obtain the camber. The acceptable amount of camber is 1/16 inch to 3/32 inch
(1.6 to 2.4 mm).
(FTR + RTR) DIVIDED BY 2 (TWO) MINUS
BTR EQUALS CAMBER
If the (BTR) distance measurement is less than
the average FTR and RTR distance measure­
ment, the camber will be positive ( + ). If the (BTR) distance measurement is greater than the average FTR and RTR distance, the camber will
be negative ( - ).
If the toe position or camber is not acceptable, a
bent or deformed rear axle shaft is most likely the cause.

TIRE
NOISE
Check tires that are damaged, unbalanced, incor­
rectly inflated. Tires that have deep treads can emit sounds like axle noise. Differentiate between tire and
axle noise during a road test. Tire noise will usually vary with different road
conditions. Tire noise is sensitive to inflation pres­
sure.
The pitch of tire noise changes when the vehi­
cle speed is varied.
Drive the vehicle over different road surfaces. Note
the changes in the noise. If the noise changes, the
tires are the source of the noise.
Refer to Group 22, Wheels and Tires for additional
information.

GEAR
AND BEARING NOISE
GEAR
NOISE
Axle gear noise can be caused by insufficient lubri­
cant. Incorrect backlash, tooth contact, or worn/dam­ aged gears can cause noise.
Gear noise usually happens at a specific speed
range. The range is 30 to 40 mph, or above 50 mph.
The noise can also occur during a specific type of driving condition. These conditions are, acceleration,
deceleration, coast, or constant load.
When road testing, accelerate 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, check for
insuf­

ficient lubricant. Incorrect ring gear backlash, or gear damage can cause noise changes.
Differential side and pinion gears can be checked
by turning the vehicle. They usually do not cause noise in straight-ahead driving. These gears are
loaded during vehicle turns. If noise does occur dur­
ing vehicle turns, the side or pinion gears could be
worn or damaged. A worn pinion gear mate shaft can also cause a snapping or a knocking noise.

BEARING NOISE
The axle shaft, differential and pinion gear bear­
ings can all produce noise when worn or damaged.
Bearing noise can be either a whining, or a growling sound.
Pinion gear bearings have a constant-pitch noise.
This noise changes only with vehicle speed. Pinion
bearing noise will be higher because it rotates at a faster rate. Drive the vehicle and load the differen­

tial.
If bearing noise occurs the pinion rear bearing is the source of the noise. If the bearing noise is heard during a coast, front bearing is the source.
Worn, damaged differential bearings usually pro­
duce a low pitch noise. Differential bearing noise is
similar to pinion bearing. The pitch of differential
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

•

REAR
SUSPENSION
AND
AXLE
3 - 55
(12) Tighten forcing screw
to
compress
the
conned

plates.
Lubricate
and
install pinion gear thrust washers with
a
small screw driver.
(13) Insert and tap
the
pinion shaft into the differ­
ential case (Fig.
13).

(14) Secure pinion shaft with
new
roll pin. Stake
roll
pin
to
differential case.
Fig.
13
Pinion
Gear
Mate
Shaft
installation

POWER-LOK
DIFFERENTIAL

SERVICE
INFORMATION Model
70
rear axles equipped with
a
Power-Lok
differential
are
optionally available
for
Ram
Truck
vehicles (Fig.
1).

FLANGE
BUTTON
BOLTS

PINION

AAATE
SHAFT
J9203-71

Fig.
1
Power-Lok
Differential

DIFFERENTIAL
NOISE
Noise complaints involving
a
Power-Lok should
be

evaluated
to
determine
the
source
of
the noise.
If a

noise occurs while
the
vehicle
is
turning,
the
proba­
ble cause
is
incorrect gear lubricant. Replace axle gear lubricant
and add
MOPAR Hypoid Gear Lubri­
cant Additive. This will correct the condition
in
most
instances. However,
if the
chatter persists, clutch
disc damage could have occurred.

WARNING:
WHEN SERVICING VEHICLES
WITH
A
POWER-LOK
DIFFERENTIAL, DO NOT USE THE EN­

GINE
TO
ROTATE THE AXLE AND
WHEELS.
BOTH
REAR
WHEELS MUST BE
RAISED
FROM THE
SUR­

FACE
AND
THE
VEHICLE SUPPORTED. POWER-

LOK
CAN
EXERT ENOUGH DRIVING FORCE
(IF

ONE
WHEEL IS
IN
CONTACT
WITH
THE SURFACE)
TO
CAUSE
THE VEHICLE TO MOVE.

DIFFERENTIAL
TEST
(1) Drive
the
vehicle
to
thoroughly warm
up the

lubricant
in
the
rear axle.
(2) Place
a
large piece
of
Kraft paper over
a

smooth Formica board. Ensure Formica board
is on a

flat and level surface.
(3) Drive
the
vehicle over
the
Formica board until
one rear wheel
is in the
center
of
the board
and
pa­

per. (4) Place
a
block
of
wood that
is 2
inches high
and

a minimum
of 3
inches wide
in
front
of
one
of
the

front tires.
(5) With
a
gradual throttle opening, attempt
to

slowly drive
the
vehicle over
the
block
of
wood.
(6)
If
the Kraft paper slips out from under the rear
wheel before
the
front tire moves over
the
block
of
wood; reposition
the
vehicle
so
paper
and
board
are
under
the
opposite rear wheel. Attempt
to
drive over
the block
of
wood
the
second time.

•

BRAKES
i - 3 BRAKE DIAGNOSIS

INDEX

page

Brake
Warning Lights
3

Diagnosing
Brake Problems .................
4

Diagnosis
Procedures
3

Low
Vacuum
Switch—Diesel
Models
3
page

Master
Cylinder/Power Booster Test
5

Power
Booster
Check
Valve Test .............
6

Power
Booster
Vacuum
Test .................
6

Testing Diesel
Engine
Vacuum
Pump
Output
.... 6

DIAGNOSIS
PROCEDURES
Brake diagnosis involves determining
if the
prob­
lem
is
related
to a
mechanical, hydraulic
or
vacuum
operated component.
A
preliminary check, road test­
ing
and
component inspection
can all be
used
to de­

termine
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 causing
a
problem. The first diagnosis step
is the
preliminary 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
the
existence
of a
problem.
Final diagnosis procedure involves road test analysis and
a
visual inspection
of
brake components.

BRAKE
WARNING LIGHTS
The
red
brake warning light
is
connected
to the

parking brake switch
and to the
pressure differential switch
in the
combination valve. The
red
light will illuminate when
the
parking
brakes
are
applied
or
when
a
fluid pressure drop
oc­
curs
in the
front
or
rear brake circuit.
The
light will
also illuminate
for
approximately
2-4
seconds
at en­

gine start
up.
This
is a
self test feature designed
to

check bulb
and
circuit operation each time
the en­

gine
is
started. The amber antilock light
is
connected
to the
anti-
lock rear brake hydraulic valve.
The
light will illu­
minate
if a
fault occurs within
the
antilock system.

LOW VACUUM SWITCH-DIESEL MODELS
On diesel models,
the red
brake warning light
is
also
used
to
alert
the
driver
of a low
brake booster vacuum
condition.
The
warning light
is in
circuit with
a
vacuum
warning switch mounted
on the
driver side fender
panel.
The
vacuum side
of the
switch
is
connected
to the

power brake booster.
The
electrical side
of the
switch
is
connected
to the
brake warning light. The
low
vacuum switch monitors booster vacuum
level whenever
the
engine
is
running.
If
booster vac­
uum falls below
8.5
inches vacuum
for a
minimum
of
10 seconds,
the
switch completes
the
circuit
to the

warning light causing
it to
illuminate.
The
warning light
is
designed
to
differentiate between
a low
vac­
uum condition
and a
hydraulic circuit fault.

PRELIMINARY
BRAKE CHECK
(1) Check condition
of
tires
and
wheels. Damaged
wheels
and
worn, damaged,
or
underinflated tires
can
cause pull, shudder, tramp,
and a
condition similar
to
grab.

(2)
If
complaint
was
based
on
noise when braking,
check suspension components. Jounce front
and
rear
of

vehicle
and
listen
for
noise that might
be
caused
by

loose, worn
or
damaged suspension
or
steering compo­

nents.

(3) Inspect brake fluid level
and
condition. Note
that
the
front disc brake reservoir fluid level will drop
in
proportion
to
normal lining wear. Also note
that brake fluid tends
to
darken over time. This
is normal
and
should
not be
mistaken
for
con­
tamination.
If the
fluid
is
still clear
and
free
of

foreign material,
it is OK.

(a)
If
fluid level
is
abnormally
low,
look
for
evi­
dence
of
leaks
at
calipers, wheel cylinders, brake-
lines
and
master cylinder.
(b)
If
fluid appears contaminated, drain
out a

sample.
If
fluid
is
separated into layers,
or
obvi­
ously contains
oil or a
substance other than brake
fluid,
the
system seals
and
cups will have
to be re­

placed
and the
hydraulic system flushed.
(4) Check parking brake operation. Verify free
movement
and
full release
of
cables
and
pedal. Also
note
if
vehicle
was
being operated with parking
brake partially applied.
(5) 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.
(6)
If
components checked appear
OK,
road test
the

vehicle.

ROAD
TESTING (1)
If
complaint involved
low
brake pedal, pump
the pedal
and
note
if the
pedal comes back
up to
nor­ mal height.
(2) Check brake pedal response with transmission
in Neutral
and
engine running. Pedal should remain
firm under steady foot pressure.

•

BRAKES
5 - 5 Disc brake rotors with excessive lateral runout or
thickness variation, or out of round brake drums are
the 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 con­
taminated lining in one caliper, seized caliper piston,
binding caliper, loose caliper, loose or corroded slide

pins,
improper brakeshoes, or a damaged rotor.
A worn, damaged wheel bearing or suspension compo­
nent are further causes of pull. A damaged front tire (bruised, ply separation) can also cause pull.
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 one of the brake units.
As the dragging brake overheats, efficiency is so
reduced that fade occurs. Since the opposite brake
unit is still functioning normally, its braking effect is
magnified. This causes pull to switch direction in fa­
vor of the normally functioning brake unit.
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
OR
PULL
Rear grab or pull is usually caused by an improperly
adjusted or seized parking brake cable, contaminated
lining, bent or binding shoes and support plates, or im­
properly assembled components. This is particularly
true when only one rear wheel is involved. 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 driv­
ing with the brakes very lightly applied for a few min­

utes.
However, if the lining is thoroughly wet and dirty,
disassembly and cleaning will be necessary.

BRAKE NOISE

Squeak/Squeal
Brake squeak or squeal may be due to linings that
are wet or contaminated with brake fluid, grease, or oil. Glazed linings and rotors with hard spots can also con­
tribute to squeak. Dirt and foreign material embedded in the brake lining can also cause squeak/squeal.
A very loud squeak or squeal is frequently a sign of
severely worn brake lining. If the lining has worn
through to the brakeshoes in spots, metal-to-metal con­
tact occurs. If the condition is allowed to continue, ro­ tors can become so scored that replacement is necessary.
Thump/Clunk

Thumping or clunk noises during braking are fre­
quently not caused by brake components. In many

cases,
such noises are caused by loose or damaged steering, suspension, or engine components. How­
ever, calipers that bind on the slide pins, or slide sur­

faces,
can generate a thump or clunk noise. Worn
out, improperly adjusted, or improperly assembled
rear brakeshoes can also produce a thump noise.

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.
Brakelining Contamination Brakelining contamination is usually a product of
leaking calipers or wheel cylinders, driving through
deep water puddles, or lining that has become cov­
ered with grease and grit during repair.
Wheel and
Tire
Problems Some conditions attributed to brake components
may actually be caused by a wheel or tire problem.
A damaged wheel can cause shudder, vibration and
pull. A worn or damaged tire can also cause pull.
Severely worn tires with very little tread left can
produce a grab-like condition as the tire loses and re­ covers traction. Flat-spotted tires can cause vibration and wheel
tramp and generate shudder during brake operation. A tire with internal damage such as a severe
bruise or ply separation can cause pull and vibration.

MASTER
CYLINDER/POWER BOOSTER TEST
(1) Start engine and check booster vacuum hose
connections. Hissing noise indicates a vacuum leak. Correct any leaks before proceeding. (2) Stop engine and shift transmission into Neu­
tral (3) Pump brake pedal until all vacuum reserve in
booster is depleted. (4) Press and hold brake pedal under light foot
pressure. (a) If pedal holds firm, proceed to step (5).
(b) If pedal does not hold firm and falls away,
master cylinder is faulty (internal leakage). (5) Start engine and note pedal action. (a) If pedal falls away slightly under light foot
pressure then holds firm, proceed to step (6). (b) If pedal is effort is high, or no pedal action is
discernible, power booster or vacuum check valve is
faulty. Install known good check valve and repeat steps (2) through (5).