1993 DODGE TRUCK Service Repair Manual

5
- 54
BRAKES

• (11) Attach adjuster cable to adjuster lever. Be
sure cable is properly routed.
(12) Adjust brakeshoes to drum with brake gauge.

BRAKE
DRUM INSTALLATION
(1) Position drum on axle housing.
(2) Install bearing and inner nut. Adjust bearing
as described in Group 3. (3) Install locking washer and outer nut. Bend
locking washer to secure it. (4) Place new gasket on hub and install axle shaft,

cones,
lock washers and nuts. (5) Install wheel and tire assembly.
(6) Remove support stands and lower vehicle.

BRAKE
DRUM
SERVICE
BRAKE DRUM REFINISHING The brake drums can be resurfaced on a drum
lathe when necessary. Initial machining cuts should
be limited to 0.12 - 0.20 mm (0.005 - 0.008 in.) at a time as heavier feed rates can produce taper and sur­
face variation. Final finish cuts of 0.025 to 0.38 mm (0.001 to 0.0015 in) are recommended and will gen­
erally provide the best surface finish.
Be sure the drum is securely mounted in the lathe
before machining operations. A damper strap should always be used around the drum to reduce vibration
and avoid chatter marks.
BRAKE DRUM REFINISH LIMITS The maximum allowable diameter of the drum
braking surface is stamped or cast into the drum outer edge (Fig. 9). Generally, a drum can be ma­
chined to a maximum of 1.5 mm (0.060 in.) oversize.
Always replace the drum if machining would cause
drum diameter to exceed indicated size limit.
BRAKE DRUM RUNOUT Measure drum diameter and runout with an accu­
rate gauge. The most accurate method of measure­
ment involves mounting the drum in a brake lathe and checking variation and runout with a dial indi­
cator.
Variations in drum diameter should not exceed
0.076 mm (0.003 in). Drum runout should not exceed
0.20 mm (0.008 in.) out of round. Refinish the drum
if runout or variation exceed these values.

WHEEL
CYLINDER REMOVAL
(1) Raise and support vehicle.
(2) Remove brake drum and brakeshoes as de­
scribed in this section. (3) Remove anchor bolt and nut and remove
washer, spring, parking brake lever, adjuster cable, cam plate and anchor pin bushing. (4) Loosen brakeline at wheel cylinder.
(5) Remove wheel cylinder bolts. Fig. 9 Location Of Brake
Drum
Maximum Allowable
Diameter (6) Disconnect brakeline and remove wheel cylin­
der.

WHEEL
CYLINDER OVERHAUL

WHEEL CYLINDER DISASSEMBLY (1) Remove push rods and boots (Fig. 10).
(2) Press pistons, cups and spring and expander
from cylinder bore. (3) Remove bleed screw.

Fig.
10
Wheel
Cylinder
Components

CLEANING AND INSPECTION Clean the cylinder and pistons with clean brake
fluid or brake cleaner only. Do not use any other cleaning agents. Dry the cylinder and pistons with
compressed air. Do not use rags or shop towels to dry
the cylinder components. Lint from such materials can adhere to the cylinder bores and pistons.

•

BRAKES
5 - 55 Inspect the cylinder bore. Light discoloration and
dark stains in the bore are normal and will not im­
pair cylinder operation. If desired, the bore can be lightly polished but only with crocus cloth. Replace
the cylinder if the bore is scored, pitted or heavily corroded. Honing the bore to restore the surface is not recommended.
Inspect the cylinder pistons. The piston surfaces
should be smooth and free of scratches, scoring and
corrosion. Replace the pistons if worn, scored, or cor­
roded. Do attempt to restore the surface by sanding or polishing.
Discard the old piston cups and the spring and ex­
pander. These parts are not reusable. The original
dust boots may be reused but only if they are in good condition.

ASSEMBLING
WHEEL CYLINDER
(1) Lubricate wheel cylinder bore, pistons, piston
cups and spring and expander with ^clean brake fluid. (2) Install first piston in cylinder bore. Then in­
stall cup in bore and against piston. Be sure lip of
piston cup is facing inward (toward spring and
expander) and flat side is against piston.
(3) Install spring and expanders followed by re­
maining piston cup and piston.
(4) Install boots on each end of cylinder and insert
push rods in boots.

(5)
Install cylinder bleed screw.

WHEEL
CYLINDER INSTALLATION
(1) Start brakeline into cylinder.
(2) Position cylinder on support plate and install
cylinder attaching bolts. (3) Tighten brakeline fitting and cylinder attach­
ing bolts. (4) Install anchor pin bushing, cam plate, adjuster
cable, parking brake lever, spring washer and anchor
bolt and nut.
(5) Install brakeshoes and brake drum as described
in this section. (6) Install axle shaft.
(7) Install wheel and tire.
(8) Remove supports and lower vehicle.

SUPPORT
PLATE REMOVAL
(1) Raise and support vehicle.
(2) Remove wheel and tire.
(3) Remove axle shaft.
(4) Remove brake drum, brake shoes and wheel
cylinder as described in this section. (5) Remove bolts/nuts attaching support plate to
axle and remove support plate.

SUPPORT PLATE INSTALLATION
(1) Transfer wheel cylinder and parking brake le­
ver components to replacement support plate. (2) Position support plate on axle and install at­
taching bolts/nuts. (3) Lubricate shoe contact surfaces of support plate
with Mopar multi-purpose, or high temperature bear­ ing grease. (4) Install brakeshoes. Adjust shoes to drum with
brake gauge. (5) Install brake drum.
(6) Install axle shaft.
(7) Install wheel and tire.
(8) Remove supports and lower vehicle.

5
- 56
BRAKES

•
PARKING
BRAKES

GENERAL INFORMATION
The parking brake mechanism
on AD
models
is a

three cable system operated
by a
foot pedal assembly
(Figs.
1 and 2).
The foot pedal
is
mounted
on the
driver side cowl
panel.
The
front cable
is
attached
to the
pedal assem­
bly.
An
intermediate cable connects
the
front cable
to

the rear cables.
An
equalizer
and
ratio lever connect
the rear cables
to the
intermediate cable.
The
rear
cables
are
connected
to the
secondary brakeshoes
by
a lever attached
to
each shoe.

PARKING BRAKE CABLE ADJUSTMENT
(1) Adjust rear drum brakes before adjusting park­
ing brake cables. (2) Release parking brakes fully.
(3) Raise vehicle.
(4) Loosen adjusting
nut on
front cable until there
is slack
in all
cables. (5) Rotate rear wheels
and
tighten cable adjusting
nut until slight drag
is
created
at
wheels.
(6)
Continue rotating rear wheels
and
loosen cable
adjusting
nut
until
all
drag
is
eliminated. (7) Back
off
cable adjusting
nut an
additional
two

full turns.
(8)
Apply parking brake several times.
(9) Release parking brakes. Then verify that rear
wheels rotate freely with
no
evidence
of
drag. (10) Lower vehicle.

REAR
CABLE REPLACEMENT
REAR CABLE
REMOVAL
(1) Release parking brakes fully.
(2) Raise vehicle.
(3) Remove adjusting
nut
from front cable.
(4) Remove rear wheels.
(5) Remove brake drums.

(6)
Remove brakeshoes
and
parking brake strut
and spring. (7) Disconnect cable from parking brake lever
on

secondary brakeshoe.
(8)
Compress cable retainer tabs
and
remove cable
from support plate.
(9) Remove cable from guides
and
retaining clips.
(10) Disconnect cable from equalizer
and
ratio
le­

ver.
(11) Remove cable.

REAR CABLE
INSTALLATION
(1) Insert cable through support plate hole
and

seat cable. (2) Connect cable
to
lever
on
secondary brakeshoe.
(3) Install brakeshoes, parking brake strut
and

spring, shoe return
and
holddown springs
and
self
adjuster components.

(4)
Install cable
in
cable guide
and
install cable
re­

taining clips,
if
equipped. (5) Connect cable
to
ratio lever
and
equalizer.

(6)
Adjust rear brakes
and
install brake drum
and

wheel. (7) Adjust parking brake cable.

FRONT CABLE REPLACEMENT

FRONT
CABLE
REMOVAL
(1) Remove front cable adjusting
nut.

(2) Remove clip securing cable
to
anchor bracket
and slide cable
out of
bracket.
(3) Remove retainer attaching cable
to
pedal
as­

sembly frame.

(4)
Disengage cable from pedal clevis.
(5) Remove cable grommet
(or
seal) from floor
pan.

(6)
Remove front cable.

FRONT
CABLE
INSTALLATION
(1) Insert cable through floor
pan.
(2) Connect cable
to
pedal clevis
and
install cable
retainer.
(3) Seat cable grommet
(or
seal)
in
floorpan.

(4)
Route cable
to
anchor bracket
and
intermediate
cable.

(5)
Secure cable
in
anchor bracket with U-clip.

(6)
Connect cable
to
adjusting link
and
install
ca­

ble adjusting
nut.
(7)
Adjust rear brakeshoes,
if
necessary.
(8) Adjust parking brake cable
as
described
in
this
section.

INTERMEDIATE
CABLE REPLACEMENT
(1) Remove adjusting
nut
from front cable.
(2) Disengage intermediate cable from ratio lever
or cable equalizer.
(3)
Remove cable.

(4)
Connect
new
cable
to
ratio lever
or
cable equal­
izer.
(5)
Connect cable
to
adjusting link.

(6)
Insert front cable
in
adjusting link
and
install
cable adjusting
nut.
(7)
Adjust brakeshoes
if
necessary.
(8) Adjust parking brake cable
as
described
in
this
section.

•

BRAKES
5
-
57

PAGE
1
OF
2
RR05E103

i - i8
BRAKES

CABLE
INTERMEDIATE
BRACKET
BOLT

VIEW
E
Fig. 2 Parking Brake Cable Attachment

•

BRAKES
5 - 59
REAR
WHEEL
ANTILOCK
(RWAL) BRAKES

page

Antilock
Component Service
63

Antilock
Service Diagnosis
62
Checking
Speed
Sensor
Air
Gap .............
64

Clearing
A
Fault
Code .....................
63
Electronic
Control
Module Replacement
........
64

Fault Code Capacity
62

Fault Code
Identification
62
page

General
Information
59
Hydraulic Valve Replacement
63

Speed
Sensor
Replacement
................
64

System
Components
......................
59

System
Fault
Codes
......................
62

System
Operation
61

GENERAL
INFORMATION
A rear wheel antilock brake system
is
standard
equipment
on all AD
models.
It is an
electronically operated system designed
to
retard rear wheel lockup
during periods
of
high wheel slip
and
deceleration.
Retarding lockup
is
accomplished
by
modulating
fluid pressure
to the
rear brake units. Rear brake fluid apply pressure
is
modulated
ac­

cording
to
wheel speed, degree
of
wheel slip
and
rate
of deceleration.
A
sensor located
in the
rear axle
housing converts differential rotating speed into elec­
tronic signals.
The
signals
are
transmitted
to the
electronic brake control module
for
processing.
The

control unit determines rate
of
deceleration
and

wheel slip from these signals.
SYSTEM
COMPONENTS

Basic system components include
an
electronic
brake control module,
a
hydraulic pressure control
valve,
a
speed sensor
and
exciter ring
and an
anti- lock warning lamp (Fig.
1).
A standard master cylinder
and
vacuum power
brake booster
are
used
for all
applications.

ANTILOCK ELECTRONIC CONTROL MODULE
The electronic module controls
all
phases
of
anti-
lock mode brake operation.
The
module
is
separate
from other electrical circuits
in the
vehicle
and
oper­ ates independently.
The module
is
located
on the
passenger side cowl
panel under
the
dash
(Fig.
2).
The
system hydraulic
valve, speed sensor
and
indicator lamps
are all in cir-
SPEED

SENSOR

EXCITER RING j3l
a

RWAL
ELECTRONIC

CONTROL MODULE AXLE

HOUSING HYDRAULIC
VALVE

J9005-96
Fig.
1
Rear
Wheel
Antilock
Brake
System
(RWAL)

5
- 60
BRAKES

Fig.
2
Antilock
Electronic Control
Module
RWAL
HYDRAULIC
VALVE
The hydraulic valve is a pressure controlling device
and is operated by the electronic module. The valve
controls fluid apply pressure to the rear brake units
during antilock mode braking (Fig. 3). The valve is
mounted on the driver side frame rail at the front of
the vehicle.
The valve contains an accumulator, an isolation
valve and a dump valve. The accumulator is operated
by fluid and spring pressure. The two valves are op­ erated by electrical solenoids. The solenoids are oper­
ated by the antilock control module.
The hydraulic valve components are inactive dur­
ing periods of normal braking effort. The valve com­
ponents are activated only when braking effort and rate of wheel slip and deceleration are high (antilock

mode).

During normal braking the valve allows free flow
of brake fluid to the rear brake units. In antilock
mode, the valve will decrease, hold or increase fluid
apply pressure as needed. •

CONNECTOR
J9005-99
Fig. 3 RWAL Hydraulic Valve
SPEED
SENSOR
AND EXCITER RING
A single pole, variable reluctance speed sensor is
used to transmit speed and rate of deceleration in­
puts to the control module (Fig. 4). The sensor is ac­
tuated by an exiter ring on the differential case.
The sensor is mounted at the top of the rear axle
housing directly over the gear-type exiter ring (Fig.
1).
The exciter ring is pressed onto the differential
case next to the ring gear.
The exciter ring is the sensor trigger mechanism.
As the ring rotates, the teeth on the ring will inter­
rupt the magnetic field around the sensor pole. The rate of interruption is converted into speed signals
which are transmitted to the control module.

Fig.
4
RWAL Speed Sensor

ANTILOCK INDICATOR LAMP The amber colored indicator lamp is located in the
instrument panel. The lamp alerts the driver if a sys­
tem fault occurs.
The antilock and brake warning lamps are both in
circuit with the electronic module. The module will
cuit with the module. The module contains a micro­
processor that operates the system and performs system diagnostic checks. Speed sensor inputs are continuously monitored
and interpreted by the module. The module deter­
mines wheel speed and rate of deceleration from
these inputs and activates the appropriate solenoid in the hydraulic valve when necessary.
The module microprocessor also contains a self test
program. The program is activated when the ignition switch is turned to the On position. In this mode, the
module checks indicator light operation, the system
electrical circuits and the pressure limiting valve so­
lenoids.
The brake warning and antilock indicator lamps
are illuminated for approximately two seconds dur­
ing the system self test cycle.

•

BRAKES
5 - 61 cause the two lamps to illuminate or flash to alert
the driver that system operation is either normal or
that a fault has occurred.

SYSTEM
OPERATION
During light brake applications, rear wheel decel­
eration and/or slip is not sufficient to activate the an­
tilock system. Brake fluid apply pressure at the rear
wheels is normal. However, when braking effort, de­ gree of wheel slip and rate of deceleration approach
programmed limits, sensor inputs will cause the module to activate the system.

Normal
Braking
Mode
In normal braking mode, the hydraulic valve com­
ponents are inactive. The isolation valve is open and
the dump valve and accumulator are closed. Fluid
flows unimpeded through the isolation valve directly
to the rear wheel cylinders (Fig. 5).
ACCUMULATOR
CLOSED

ACCUMULATOR
CLOSED

0 m
m
0 UUb Ft

L DUMP
VALVE

CLOSED
SPRING
ISOLATION
VALVE
OPEN
FROM

MASTER

CYLINDER TO
REAR
BRAKES

J9005-93

Fig.
5
Valve
Position And Fluid Flow-Normal
Braking

Start
Of
Antilock
Mode
Braking
When high pedal effort braking occurs, the de­
crease in exiter wheel rotating speed is converted
into an electronic signal by the sensor. This signal is
transmitted to and processed by, the control module.
The module determines that acceptable limits of wheel slip/deceleration are about to be exceeded. The
module activates the hydraulic valve at this point.
The control module transmits a signal to the isola­
tor valve solenoid which closes the valve (Fig. 6). Closing the valve prevents further fluid flow to the
rear wheel cylinders. This action isolates the rear
brakes from the master cylinder. The net effect is to decrease rear brake apply pressure to the point
where the wheels will continue to rotate and not lock.

Additional
Pressure
Relief
During
Antilock
Mode
Braking
The dump valve and accumulator are hydraulically
connected and serve as additional pressure limiting
ISOLATION
VALVE

CLOSED

FROM

MASTER

CYLINDER
DUMP
VALVE

CLOSED

TO
REAR
BRAKES
J9005-94

Fig.
6
Valve
Position And Fluid Flow At
Start
Of
Anti-Lock
Mode
Braking

devices. The accumulator and dump valve remain
closed during initial closing of the isolation valve.
However, if pressure exerted by fluid captured in the
wheel cylinders and lines is high enough to lock the
wheels, the dump valve and accumulator are acti­ vated (Fig. 7).
When captured fluid pressure is high, the control
module opens the dump valve (Fig. 7). Since the
dump valve is connected to the accumulator, a por­
tion of the captured fluid is diverted through the
valve and into the accumulator. The amount of fluid diverted is sufficient to reduce apply pressure to an­
tilock levels.
When rear brake pressure requirements return to
normal levels, the accumulator spring closes the ac­ cumulator. Fluid in the accumulator is forced out
and back into the hydraulic system.

ACCUMULATOR OPEN DUMP
VALVE
OPEN ISOLATION
VALVE

CLOSED

FROM

MASTER

CYLINDER
FROM
REAR
BRAKES
TO ACCUMULATOR
J9005-95

Fig.
7 Dump
Valve
And
Accumulator
Position In
Pressure
Relief
Mode