ECU DODGE RAM 1500 1998 2.G Owner's Manual

INSTALLATION
(1) Raise axle with lift and align to the leaf spring
centering bolts.
(2) Install axle U-bolts and tighten to 149 N´m
(110 ft. lbs.).
(3) Install shock absorbers to axle and tighten to
specification.
(4) Install all brake components.
(5) Align propeller shaft and pinion companion
flange reference marks and tighten companion flange
bolts to 115 N´m (85 ft. lbs.).
(6) Install the wheels and tires.
(7) Fill differential to specifications.
(8) Remove lift from axle and lower the vehicle.
ADJUSTMENTS
Ring and pinion gears are supplied as matched
sets. Compensation for pinion depth variance is
achieved with a select shim, located between the rear
pinion bearing and pinion gear head.
PINION DEPTH MEASUREMENT AND ADJUSTMENT
Measurements are taken with pinion bearing cups
and pinion bearings installed in the housing. Take
measurements with Pinion Gauge Set and Dial Indi-
cator C-3339 (Fig. 3).(1) Assemble Pinion Height Block 6739, Pinion
Block 8897 and rear pinion bearing onto Screw 6741
(Fig. 3).
(2) Insert assembled height gauge components,
rear bearing and screw into the housing through pin-
ion bearing cups (Fig. 4).
(3) Install front pinion bearing and Cone-nut 6740
onto the screw. Tighten cone-nut until Torque To
Rotate the screw is 1.7-2.26 N´m (15-20 in. lbs.) (Fig.
3).
(4) Place Arbor Discs 8289 on Arbor D-115-3 in
position in the housing side bearing cradles (Fig. 5).
(5) Install differential bearing caps on arbor discs
and snug the bearing cap bolts. Then cross tighten
cap bolts to 281 N´m (207 ft. lbs.).
NOTE: Arbor should rotate freely in the arbor discs.
(6) Assemble Dial Indicator C-3339 into Scooter
Block D-115-2 and secure set screw.
(7) Position Scooter Block/Dial Indicator flush on
the pinion height block. Hold scooter block and zero
the dial indicator.
(8) Slowly slide the scooter block across the pinion
height block over to the arbor (Fig. 6). Move the
scooter block till dial indicator crests the arbor, then
record the highest reading.
(9) Select a shim equal to the dial indicator read-
ing.
(10) Install the select shim between the rear pin-
ion bearing and the pinion gear head.
Fig. 3 PINION GEAR DEPTH GAUGE TOOLS
1 - DIAL INDICATOR
2 - ARBOR
3 - PINION HEIGHT BLOCK
4 - CONE
5 - SCREW
6 - PINION BLOCK
7 - SCOOTER BLOCK
8 - ARBOR DISC
Fig. 4 PINION HEIGHT BLOCK
1 - PINION BLOCK
2 - PINION HEIGHT BLOCK
3 - 144 REAR AXLE - 11 1/2 AADR
REAR AXLE - 11 1/2 AA (Continued)

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. However,
calipers that bind on the slide surfaces can generate
a thump or clunk noise.
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.
(1) Remove reservoir filler caps and fill reservoir.
(2) If calipers were 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.
NOTE: Bleed procedure should be in this order (1)
Right rear (2) Left rear (3) Right front (4) Left front.(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.
(5) Before moving the vehicle verify the pedal is
firm and not mushy.
(6) Top off the brake fluid and install the reservoir
cap.
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.
Follow the manufacturers instructions carefully
when using pressure equipment. Do not exceed the
tank manufacturers pressure recommendations. Gen-
erally, a tank pressure of 15-20 psi is sufficient 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.
SPECIAL TOOLS
BASE BRAKES
Fig. 1 Bleed Hose Setup
1 - BLEED HOSE
2 - FLUID CONTAINER PARTIALLY FILLED WITH FLUID
INSTALLER, BRAKE CALIPER DUST BOOT C-4340
INSTALLER, BRAKE CALIPER DUST BOOT
C-3716-A
DRBRAKES - BASE 5 - 5
BRAKES - BASE (Continued)

(7) Remove the mounting bolt for the brake hose
at the axle (Fig. 8).
(8) Remove the hose.
REMOVAL - REAR TUBE / HOSE ASSEMBLY
(1) Install prop rod on the brake pedal to keep
pressure on the brake system.
(2) Raise and support the vehicle.
(3) Remove the brake line located at the axle.
(4) Remove the mounting bolt for the brake hose
at the axle (Fig. 9).
(5) Remove the banjo bolt at the caliper (Fig. 9).
(6) Remove the hose.
REMOVAL - FRONT HOSE
(1) Install a prop rod on the brake pedal to keep
pressure on the brake system.
(2) Raise and support vehicle.
(3) Remove the tire and wheel assembly.
(4) Remove the brake hose from the brake line
located at the frame (Fig. 10).
(5) Remove the brake hose banjo bolt at the caliper
(Fig. 10).
(6) Remove the mounting bolt securing the brake
hose to the frame and remove the wheel speed sensor
wire from the brake hose (Fig. 10).
(7) Remove the hose.
INSTALLATION
INSTALLATION - REAR BRAKE HOSE
(1) Install the hose.
(2) Install the mounting bolt for the brake hose at
the axle (Fig. 8).
(3) Install the two brake lines at the bottom of the
hose located at the axle (Fig. 8).
(4) Install the vent tube (Fig. 8).
(5) Install the brake hose clip at the top of the
hose located at the frame (Fig. 7).
(6) Install the brake line to the hose at the frame
(Fig. 7).
(7) Lower the vehicle and remove the support.
(8) Remove the prop rod.
(9) Bleed the brake system (Refer to 5 - BRAKES -
STANDARD PROCEDURE).
Fig. 8 REAR HOSE
1 - BRAKE HOSE
2 - VENT HOSE
3 - BRAKE LINES
Fig. 9 BRAKE LINE WITH RUBBER HOSE
1 - BANJO BOLT
2 - MOUNTING BOLT
3 - REAR TUBE / HOSE ASSEMBLY
Fig. 10 BRAKE HOSE MOUNTED PASSENGER SIDE
1 - MOUNTING BOLT
2 - BRAKE HOSE
3 - BANJO BOLT
4 - WHEEL SPEED SENSOR WIRE
5 - 12 BRAKES - BASEDR
BRAKE LINES (Continued)

rotor. At the same time, fluid pressure within the pis-
ton bore forces the caliper to slide inward on the
mounting bolts. This action brings the outboard
brake pad lining into contact with the outer surface
of the disc brake rotor.
In summary, fluid pressure acting simultaneously
on both piston and caliper, produces a strong clamp-
ing action. When sufficient force is applied, friction
will attempt to stop the rotors from turning and
bring the vehicle to a stop.
Application and release of the brake pedal gener-
ates only a very slight movement of the caliper and
piston. Upon release of the pedal, the caliper and pis-
ton return to a rest position. The brake pads do not
retract an appreciable distance from the rotor. In
fact, clearance is usually at, or close to zero. The rea-
sons for this are to keep road debris from getting
between the rotor and lining and in wiping the rotor
surface clear each revolution.
The caliper piston seal controls the amount of pis-
ton extension needed to compensate for normal lining
wear.
During brake application, the seal is deflected out-
ward by fluid pressure and piston movement (Fig.
25). When the brakes (and fluid pressure) are
released, the seal relaxes and retracts the piston.
The amount of piston retraction is determined by
the amount of seal deflection. Generally the amountis just enough to maintain contact between the pis-
ton and inboard brake pad.
REMOVAL
REMOVAL - FRONT
CAUTION: Never allow the disc brake caliper to
hang from the brake hose. Damage to the brake
hose will result. Provide a suitable support to hang
the caliper securely.
(1) Install prop rod on the brake pedal to keep
pressure on the brake system.
(2) Raise and support the vehicle.
(3) Remove the tire and wheel assembly.
(4) Compress the disc brake caliper.
(5) Remove the banjo bolt and discard the copper
washer.
(6) Remove the caliper slide bolts.
(7) Remove the disc brake caliper (Fig. 26) or (Fig.
27).
REMOVAL - REAR
CAUTION: Never allow the disc brake caliper to
hang from the brake hose. Damage to the brake
hose will result. Provide a suitable support to hang
the caliper securely.
(1) Install prop rod on the brake pedal to keep
pressure on the brake system.
(2) Raise and support vehicle.
(3) Remove the wheel and tire assembly.
(4) Drain small amount of fluid from master cylin-
der brake reservoir with suction gun.
(5) Remove the brake hose banjo bolt and discard
the copper washers if replacing caliper (Fig. 28).
Fig. 24 Brake Caliper Operation
1 - CALIPER
2 - PISTON
3 - PISTON BORE
4 - SEAL
5 - INBOARD SHOE
6 - OUTBOARD SHOE
Fig. 25 Lining Wear Compensation By Piston Seal
1 - PISTON
2 - CYLINDER BORE
3 - PISTON SEAL BRAKE PRESSURE OFF
4 - CALIPER HOUSING
5 - DUST BOOT
6 - PISTON SEAL BRAKE PRESSURE ON
DRBRAKES - BASE 5 - 17
DISC BRAKE CALIPERS (Continued)

INSTALLATION
INSTALLATION - FRONT
NOTE: Install a new copper washers on the banjo
bolt when installing
(1) Install the disc brake caliper (Fig. 26) or (Fig.
27).
CAUTION: Verify brake hose is not twisted or
kinked before tightening fitting bolt.
(2) Install the banjo bolt with new copper washers
to the caliper. Tighten to 27 N´m (20 ft. lbs.)
(3) Install the caliper slide pin bolts. tighten to 32
N´m (24 ft. lbs.)
(4) Remove the prop rod.
(5) Bleed the base brake system, (Refer to 5 -
BRAKES/HYDRAULIC/MECHANICAL - STAN-
DARD PROCEDURE).
(6) Install the tire and wheel assembly, (Refer to
22 - TIRES/WHEELS/WHEELS - STANDARD PRO-
CEDURE).
(7) Lower the vehicle.
INSTALLATION - REAR
(1) Install caliper to the caliper adapter.
(2) Coat the caliper mounting slide pin bolts with
silicone grease. Then install and tighten the bolts to
15 N´m (11 ft. lbs.).
(3) Install the brake hose banjo bolt if removed.
(4) Install the brake hose to the caliper withnew
seal washersand tighten fitting bolt to 27 N´m (245
in. lbs.).CAUTION: Verify brake hose is not twisted or
kinked before tightening fitting bolt.
(5) Remove the prop rod from the vehicle.
(6) Bleed the base brake system,(Refer to 5 -
BRAKES - STANDARD PROCEDURE) OR (Refer to
5 - BRAKES - STANDARD PROCEDURE).
(7) Install the wheel and tire assemblies (Refer to
22 - TIRES/WHEELS/WHEELS - STANDARD PRO-
CEDURE).
(8) Remove the supports and lower the vehicle.
(9) Verify a firm pedal before moving the vehicle.
DISC BRAKE CALIPER
ADAPTER
REMOVAL
REMOVAL - FRONT
(1) Raise and support the vehicle.
(2) Remove the tire and wheel assembly.
(3) Remove the disc brake caliper (Refer to 5 -
BRAKES/HYDRAULIC/MECHANICAL/DISC
BRAKE CALIPERS - REMOVAL).
(4) Remove the bolts securing the caliper adapter
to the steering knuckle (Fig. 38)
(5) Remove the caliper adapter.
REMOVAL - REAR
(1) Raise and support the vehicle.
(2) Remove the wheel and tire assembly.
(3) Drain a small amount of fluid from master cyl-
inder brake reservoir with acleansuction gun.
Fig. 37 Seating Dust Boot
1 - HANDLE
2 - CALIPER
3 - DUST BOOT INSTALLER
Fig. 38 CALIPER ADAPTER
1 - CALIPER ASSEMBLY
2 - MOUNTING BOLT
3 - DISC BRAKE ROTOR
DRBRAKES - BASE 5 - 21
DISC BRAKE CALIPERS (Continued)

(4) Bottom the caliper pistons into the caliper by
prying the caliper over.
(5) Remove the caliper slide bolts.
(6) Remove the disc brake caliper from the mount.
CAUTION: Never allow the disc brake caliper to
hang from the brake hose. Damage to the brake
hose will result. Provide a suitable support to hang
the caliper securely.
(7) Remove the inboard and outboard brake pads
(Fig. 39).
(8) Remove the anti-rattle clips (Fig. 39).
(9) Remove the caliper adapter mounting bolts
(Fig. 39).
(10) Remove the caliper adapter.
INSTALLATION
INSTALLATION - FRONT
(1) Install the caliper adapter to the steering
knuckle (Fig. 38).
(2) Install the caliper adapter mounting bolts and
tighten to 176 N´m (130 ft.lbs.) (Fig. 38).
(3) Install the disc brake caliper (Refer to 5 -
BRAKES/HYDRAULIC/MECHANICAL/DISC
BRAKE CALIPERS - INSTALLATION).
(4) Install the tire and wheel assembly (Refer to 22
- TIRES/WHEELS/WHEELS - STANDARD PROCE-
DURE).
(5) Remove the support and lower the vehicle.
INSTALLATION - REAR
(1) Install the caliper adapter mounting bolts.
Tighten the mounting bolts to 135 N´m (100 ft.lbs)
(Fig. 39).(2) Install the anti-rattle clips (Fig. 39).
(3) Install the inboard and outboard pads (Fig. 39).
(4) Install the caliper mounting bolts.
(5) Install the tire and wheel assembly
DISC BRAKE CALIPER
ADAPTER MOUNT
REMOVAL - REAR
(1) Remove wheel and tire assembly.
(2) Remove the disc brake caliper (Refer to 5 -
BRAKES/HYDRAULIC/MECHANICAL/DISC
BRAKE CALIPERS - REMOVAL).
(3) Remove the caliper adapter (Refer to 5 -
BRAKES/HYDRAULIC/MECHANICAL/DISC
BRAKE CALIPER ADAPTER - REMOVAL).
(4) Remove the rotor (Refer to 5 - BRAKES/HY-
DRAULIC/MECHANICAL/ROTORS - REMOVAL).
(5) Remove the axle shaft (Refer to 3 - DIFFER-
ENTIAL & DRIVELINE/REAR AXLE - 9 1/4/AXLE
SHAFTS - REMOVAL).
(6) Remove the park brake shoes (Refer to 5 -
BRAKES/PARKING BRAKE/SHOES - REMOVAL).
(7) Remove the parking brake cable from the
brake lever.
(8) Remove the bolts attaching the support plate to
the axle and remove the support plate (Fig. 65).
(9) Remove the caliper adapter mount from the
axle housing (Fig. 40).
INSTALLATION
(1) Install the caliper adapter mount on the axle
housing (Fig. 40).
(2) Install support plate on axle flange (Fig. 66).
Tighten attaching bolts to 115 N´m (85 ft. lbs.).
Fig. 39 CALIPER MOUNT
1 - DISC BRAKE PADS
2 - ANTI-RATTLE CLIPS
3 - CALIPER ADAPTER
4 - MOUNTING BOLTS
Fig. 40 CALIPER ADAPTER MOUNT - REAR
1 - CALIPER ADAPTER MOUNT
2 - AXLE TUBE
3 - MOUNTING STUDS
5 - 22 BRAKES - BASEDR
DISC BRAKE CALIPER ADAPTER (Continued)

(9)On vehicles equipped with adjustable
brake pedal.Reconnect the electrical connector to
the motor and the adjuster cable at the pedal.
(10) Install the steering column opening cover
(Refer to 23 - BODY/INSTRUMENT PANEL/STEER-
ING COLUMN OPENING COVER - INSTALLA-
TION).
(11) Reconnect the negative battery cable.
POWER BRAKE BOOSTER
DESCRIPTION
All models use a tandem diaphragm, power brake
booster.
NOTE: The power brake booster is not a repairable
component. The booster must be replaced as an
assembly if diagnosis indicates a malfunction has
occurred.
OPERATION
The booster unit consists of a single housing
divided into two by a tandem diaphragm. The outer
edge of the diaphragm is secured to the housing. The
booster push rod, which connects the booster to the
brake pedal and master cylinder, is attached to the
center of the diaphragm. A check valve is used in the
booster outlet connected to the engine intake mani-
fold. Power assist is generated by utilizing a combi-
nation of vacuum and atmospheric pressure to boost
brake assist.
REMOVAL
(1) Remove master cylinder. (Refer to 5 - BRAKES/
HYDRAULIC/MECHANICAL/MASTER CYLINDER -
REMOVAL).
(2) Disconnect vacuum line at booster.
(3) Remove clip securing booster push rod to brake
pedal (Refer to 5 - BRAKES/HYDRAULIC/MECHAN-
ICAL/PEDAL - REMOVAL). (Fig. 53).
(4) Remove the nuts from the booster mounting
studs (Fig. 53).
(5) Remove the booster and gasket from front cowl
panel.
INSTALLATION
(1) Guide the booster studs into the cowl panel
holes and seat the booster on the panel (Fig. 53).
(2) Install and tighten new booster attaching nuts
to 28 N´m (250 in. lbs.).
(3) Install the booster push rod on brake pedal and
install clip (Fig. 53).
(4) Install the booster check valve if removed and
connect the vacuum hose to the check valve.
(5) Install the master cylinder. (Refer to 5 -
BRAKES/HYDRAULIC/MECHANICAL/MASTER
CYLINDER - INSTALLATION).
(6) Fill and bleed the brake system. (Refer to 5 -
BRAKES - STANDARD PROCEDURE).
Fig. 52 PEDAL ASSEMBLY (ADJUSTABLE PEDALS
SHOWN)
1 - ADJUSTABLE PEDAL MOTOR
2 - PEDAL ASSEMBLY BRACKET
3 - MOUNTING NUT
4 - BRAKE & ACCELERATOR PEDAL
5 - BRAKE BOOSTER MOUNTING STUDS
Fig. 53 POWER BRAKE BOOSTER
1 - MOUNTING NUT
2 - POWER BRAKE BOOSTER
DRBRAKES - BASE 5 - 29
PEDAL (Continued)

RELEASE HANDLE
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Reach under the driver side outboard end of
the instrument panel to access and unsnap the plas-
tic retainer clip that secures the park brake release
linkage rod to the park brake mechanism on the left
cowl side inner panel.
(3) Disengage the park brake release linkage rod
end from the park brake mechanism.
(4) Lift the park brake release handle to access
and unsnap the plastic retainer clip that secures the
park brake release linkage rod to the lever on the
back of the park brake release handle.
(5) Lower the park brake release handle and reach
under the driver side outboard end of the instrument
panel to disengage the park brake release linkage
rod end from the lever on the back of the park brake
release handle.
(6) Lift the park brake release handle to access the
handle mounting bracket.
(7) Using a trim stick or another suitable wide
flat-bladed tool, gently pry each of the park brake
release handle mounting bracket latch tabs away
from the retaining notches in the instrument panel
receptacle (Fig. 86).
(8) With both of the park brake release handle
mounting bracket latches released, slide the handle
and bracket assembly down and out of the instru-
ment panel receptacle.
INSTALLATION
(1) Position the park brake release handle to the
instrument panel.
(2) Slide the handle and bracket assembly up into
the instrument panel receptacle until both of the
park brake release handle mounting bracket latches
are engaged with the notches in the instrument
panel receptacle.
(3) Lower the park brake release handle and reach
under the driver side outboard end of the instrument
panel to engage the park brake release linkage rod
end with the lever on the back of the park brake
release handle.
(4) Lift the park brake release handle to access
and snap the plastic retainer clip that secures the
park brake release linkage rod to the lever on the
back of the park brake release handle over the link-
age rod.
(5) Reach under the driver side outboard end of
the instrument panel to access and engage the park
brake release linkage rod end to the park brake
mechanism.
(6) Snap the plastic retainer clip that secures the
park brake release linkage rod to the park brake
mechanism on the left cowl side inner panel over the
linkage rod.
(7) Reconnect the battery negative cable.
Fig. 85 Adjustment Mark
1 - TENSIONER CABLE BRACKET
2 - TENSIONER
3 - CABLE CONNECTOR
4 - 6.35mm
(1/4 IN.)
5 - ADJUSTER NUT
Fig. 86 Park Brake Release Handle Remove/Install
1 - CLIP
2 - ROD
3 - MOUNTING BRACKET
4 - TRIM STICK
5 - LATCH TABS
6 - PARK BRAKE RELEASE HANDLE
5 - 44 BRAKES - BASEDR
CABLE TENSIONER (Continued)

REMOVAL
(1) Remove the front rotor (Refer to 5 - BRAKES/
HYDRAULIC/MECHANICAL/ROTORS -
REMOVAL).
(2) Remove the wheel speed sensor mounting bolt
from the hub. (Fig. 3)
(3) Remove the wheel speed sensor from the hub.
(4) Remove the wiring from the clips and discon-
nect the electrical connector.
INSTALLATION
(1) Install the wiring to the clips and Reconnect
the electrical connector.
(2) Install the wheel speed sensor to the hub.
(3) Install the wheel speed sensor mounting bolt to
the hub. Tighten the bolt to 21 N´m (190 in. lbs.).
(4) Install the front rotor and brake caliper assem-
bly (Refer to 5 - BRAKES/HYDRAULIC/MECHANI-
CAL/ROTORS - INSTALLATION).
REAR WHEEL SPEED SENSOR
DIAGNOSIS AND TESTING - REAR WHEEL
ANTILOCK
Diagnosis of base brake conditions which are
mechanical in nature should be performed first. This
includes brake noise, lack of power assist, parking
brake, or vehicle vibration during normal braking.
The RWAL brake system performs several self-
tests every time the ignition switch is turned on and
the vehicle is driven. The CAB monitors the system
inputs and outputs circuits to verify the system is
operating properly. If the CAB senses a malfunction
in the system it will set a DTC into memory and trig-
ger the warning lamp.NOTE: The MDS or DRB III scan tool is used to
diagnose the RWAL system. For test procedures
refer to the Chassis Diagnostic Manual.
REMOVAL
(1) Raise the vehicle on a hoist.
(2) Remove the brake line mounting nut and
remove the brake line from the sensor stud.
(3) Remove the mounting stud from the sensor and
shield (Fig. 4).
(4) Remove the sensor and shield from the differ-
ential housing.
(5) Disconnect the sensor wire harness and remove
the sensor.
INSTALLATION
(1) Connect the harness to the sensor.Be sure
the seal is securely in place between the sensor
and the wiring connector.
(2) Install the O-ring on the sensor (if removed).
(3) Insert the sensor in the differential housing.
(4) Install the sensor shield.
(5) Install the sensor mounting stud and tighten to
24 N´m (200 in. lbs.).
(6) Install the brake line on the sensor stud and
install the nut.
(7) Lower the vehicle.
Fig. 3 WHEEL SPEED SENSOR
1 - WHEEL SPEED SENSOR MOUNTING BOLT
2 - WHEEL SPEED SENSOR
3 - HUB/BEARINGFig. 4 REAR WHEEL SPEED SENSOR
1 - WHEEL SPEED SENSOR
2 - MOUNTING BOLT
3 - AXLE HOUSING
5 - 48 BRAKES - ABSDR
FRONT WHEEL SPEED SENSOR (Continued)

PRESSURE INCREASE
The inlet valve is open and the outlet valve is
closed during the pressure increase cycle. The pres-
sure increase cycle is used to reapply thew brakes.
This cycle controls re-application of fluid apply pres-
sure.
REMOVAL
(1) Install a prop rod on the brake pedal to keep
pressure on the brake system.
(2) Disconnect the battery cables from the battery.
(3) Remove the battery.
(4) Disconnect the two electrical harness connec-
tors (Fig. 5).
(5) Remove the five brake lines from the HCU
(Fig. 5).
(6) Remove HCU/CAB mounting bolts and remove
the HCU/CAB (Fig. 5).
INSTALLATION
NOTE: If the CAB is being replaced with a new CAB
is must be reprogrammed with the use of a DRB III.
(1) Install HCU/CAB on the mounts and Tighten
the bolts to 15N´m (11 ft. lbs.) (Fig. 5).
(2) Install the five brake lines to the HCU and
tighten to 19 N´m (170 in. lbs.) (Fig. 5).
(3) Install the two electrical harness connectors to
the HCU/CAB and push down on the release to
secure the connectors.
(4) Install the battery.
(5) Install the battery cables to the battery.
(6) Remove the prop rod on the brake pedal.
(7) Bleed ABS brake system (Refer to 5 - BRAKES
- STANDARD PROCEDURE).
RWAL VALVE
DESCRIPTION
Rear Wheel Antilock (RWAL) brake system is stan-
dard equipment on 1500 series vehicles. The RWAL
brake system is designed to prevent rear wheel
lock-up on virtually all types of road surfaces. RWAL
braking is desirable because a vehicle which is
stopped without locking the rear wheels will retain
directional stability. This allows the driver to retain
greater control of the vehicle during braking.
The valve is located on the drivers side inner
fender under the hood. The valve modulates hydrau-
lic pressure to the rear brakes.
The RWAL components include:
²RWAL Valve
²Controller Antilock brake (CAB)
²Rear Wheel Speed Sensor (WSS)
OPERATION
When the brakes are applied, hydraulic fluid is
routed from the master cylinder's secondary circuit to
the RWAL valve. From there hydraulic fluid is routed
to the rear brakes. The Controller Antilock Brake
(CAB) contains an Electronic Variable Brake Propor-
tioning (EVBP) control algorithm, which proportions
the applied braking force to the rear wheels during
braking. The EVBP function of the RWAL system
takes the place of a conventional hydraulic propor-
tioning valve. The CAB monitors the rear wheel
speed through the rear wheel speed sensor and cal-
culates an estimated vehicle deceleration. When an
established deceleration threshold is exceeded, an
isolation valve is closed to hold the applied brake
pressure to the rear brakes constant. Upon further
increases in the estimated vehicle deceleration, the
isolation valve is selectively opened to increase rear
brake pressure in proportion to the front brake pres-
sure. If impending rear wheel lock-up is sensed, the
CAB signals the RWAL valve to modulate hydraulic
brake pressure to the rear wheels to prevent lock-up.
NORMAL BRAKING Since the RWAL valve also
performs the EVBP or proportioning function, vehicle
deceleration under normal braking may be sufficient
to trigger the EVBP function of the RWAL system
without full RWAL activity as would normally occur
during an impending rear wheel lock-up. As previ-
ously mentioned, the isolation valve is selectively
closed and opened to increase rear brake pressure in
proportion to the front brake pressure under EVBP
control. Slight brake pedal pulsations may be noticed
as the isolation valve is opened.
Fig. 5 HYDRAULIC CONTROL UNIT
1 - HYDRAULIC CONTROL UNIT
2 - MOUNTING BOLTS
5 - 50 BRAKES - ABSDR
HCU (HYDRAULIC CONTROL UNIT) (Continued)