2002 DODGE RAM sensor

Condition Possible Causes Correction
Axle Overheating 1. Lubricant level low. 1. Fill differential to correct level.
2. Improper grade of lubricant. 2. Fill differential with the correct fluid
type and quantity.
3. Bearing pre-loads too high. 3. Re-adjust bearing pre-loads.
4. Insufficient ring gear backlash. 4. Re-adjust ring gear backlash.
Gear Teeth Broke 1. Overloading. 1. Replace gears. Examine other
gears and bearings for possible
damage.
2. Erratic clutch operation. 2. Replace gears and examine the
remaining parts for damage. Avoid
erratic clutch operation.
3. Ice-spotted pavement. 3. Replace gears and examine
remaining parts for damage.
4. Improper adjustments. 4. Replace gears and examine
remaining parts for damage. Ensure
ring gear backlash is correct.
Axle Noise 1. Insufficient lubricant. 1. Fill differential with the correct fluid
type and quantity.
2. Improper ring gear and pinion
adjustment.2. Check ring gear and pinion contact
pattern. Adjust backlash or pinion
depth.
3. Unmatched ring gear and pinion. 3. Replace gears with a matched ring
gear and pinion.
4. Worn teeth on ring gear and/or
pinion.4. Replace ring gear and pinion.
5. Loose pinion bearings. 5. Adjust pinion bearing pre-load.
6. Loose differential bearings. 6. Adjust differential bearing pre-load.
7. Mis-aligned or sprung ring gear. 7. Measure ring gear run-out.
Replace components as necessary.
8. Loose differential bearing cap
bolts.8. Inspect differential components
and replace as necessary. Ensure
that the bearing caps are torqued tot
he proper specification.
9. Housing not machined properly. 9. Replace housing.
REMOVAL
(1) Raise and support the vehicle.
(2) Position an axle lift under the axle and secure
it to the axle.
(3) Remove the wheels and tires.
(4) Remove RWAL sensor from the differential
housing, if necessary.
(5) Remove brake hose from the axle junction
block.
(6) Disconnect parking brake cables and cable
brackets.
(7) Remove vent hose from the axle shaft tube.(8) Mark propeller shaft and yoke for installation
alignment reference.
(9) Remove propeller shaft.
(10) Remove shock absorbers from the axle brack-
ets.
(11) Remove spring clamps and spring brackets.
(12) Remove axle from the vehicle.
INSTALLATION
(1) Raise axle with lift and align to the leaf spring
centering bolts.
(2) Install spring clamps and spring brackets.
3 - 82 REAR AXLE - 267RBIBR/BE
REAR AXLE - 267RBI (Continued)

(3) Install shock absorbers and tighten to specifica-
tions.
(4) Install RWAL sensor to the differential hous-
ing, if necessary.
(5) Install parking brake cables and cable brackets
(6) Install brake hose to the axle junction block.
(7) Install axle vent hose.
(8) Install propeller shaft with reference marks
aligned.
(9) Install wheels and tires assemblies.
(10) Add gear lubricant, if necessary.
(11) Remove lift from the axle and lower the vehi-
cle.
ADJUSTMENTS
Ring and pinion gears are supplied as matched
sets only. The identifying numbers for the ring and
pinion gear are etched onto each gear (Fig. 4). A plus
(+) number, minus (±) number or zero (0) is etched
onto the pinion gear. This number is the amount (in
thousandths of an inch) the depth varies from the
standard depth setting of a pinion etched with a (0).
The standard setting from the center line of the ring
gear to the back face of the pinion is 136.53 mm
(5.375 in.). The standard depth provides the best
gear tooth contact pattern. Refer to Backlash and
Contact Pattern in this section for additional infor-
mation.
Compensation for pinion depth variance is
achieved with a select shim/oil baffle. The shims are
placed between the rear pinion bearing and the pin-
ion gear head (Fig. 5).
If a new gear set is being installed, note the depth
variance etched into both the original and replace-
ment pinion. Add or subtract this number from the
thickness of the original depth shim/oil slinger to
compensate for the difference in the depth variances.
Refer to the Depth Variance chart.
Note where Old and New Pinion Marking columns
intersect. Intersecting figure represents plus or
minus the amount needed.
Note the etched number on the face of the pinion
gear head (±1, ±2, 0, +1, +2, etc.). The numbers rep-
resent thousands of an inch deviation from the stan-
dard. If the number is negative, add that value to the
required thickness of the depth shims. If the number
is positive, subtract that value from the thickness of
the depth shim. If the number is 0 no change is nec-
essary.Fig. 4 PINION GEAR ID NUMBERS
1 - PRODUCTION NUMBERS
2 - PINION GEAR DEPTH VARIANCE
3 - GEAR MATCHING NUMBER
Fig. 5 SHIM LOCATIONS
1 - PINION GEAR DEPTH SHIM/OIL BAFFLE
2 - DIFFERENTIAL BEARING SHIM
BR/BEREAR AXLE - 267RBI 3 - 83
REAR AXLE - 267RBI (Continued)

REMOVAL
(1) Raise and support the vehicle.
(2) Position a suitable lifting device under the
axle.
(3) Secure axle to device.
(4) Remove the wheels and tires.
(5) Remove the RWAL sensor from the differential
housing, if necessary.
(6) Disconnect the brake hose at the axle junction
block.
(7) Disconnect the parking brake cables and cable
brackets.
(8)
Disconnect the vent hose from the axle shaft tube.
(9) Mark the propeller shaft and companion flange
for installation alignment reference.
(10) Remove propeller shaft.
(11) Disconnect shock absorbers from axle.
(12)
Remove the spring clamps and spring brackets.
(13) Separate the axle from the vehicle.
INSTALLATION
(1) Raise the axle with lifting device and align to
the leaf spring centering bolts.
(2) Install the spring clamps and spring brackets.
(3) Install the shock absorbers.
(4) Install the RWAL sensor to the differential
housing, if necessary
(5) Install the parking brake cables and cable
brackets.
(6)
Install the brake hose to the axle junction block.
(7) Install axle vent hose.
(8) Install the propeller shaft with reference marks
aligned.
(9) Install the wheels and tires.
(10) Add gear lubricant, if necessary. Refer to
Specifications for lubricant requirements.
(11) Remove lifting device from axle and lower the
vehicle.
ADJUSTMENTS
Ring and pinion gears are supplied as matched
sets only. The identifying numbers for the ring and
pinion gear are etched into the face of each gear (Fig.
4). A plus (+) number, minus (±) number or zero (0) is
etched into the face of the pinion gear. This number
is the amount (in thousandths of an inch) the depth
varies from the standard depth setting of a pinion
etched with a (0). The standard setting from the cen-
ter line of the ring gear to the back face of the pinion
is 147.625 mm (5.812 in.). The standard depth pro-
vides the best teeth contact pattern. Refer to Back-
lash and Contact Pattern Analysis Paragraph in this
section for additional information.
Compensation for pinion depth variance is
achieved with select shims. The shims are placed
under the inner pinion bearing cone (Fig. 5).If a new gear set is being installed, note the depth
variance etched into both the original and replace-
ment pinion gear. Add or subtract the thickness of
the original depth shims to compensate for the differ-
ence in the depth variances. Refer to the Depth Vari-
ance charts.
Note where Old and New Pinion Marking columns
intersect. Intersecting figure represents plus or
minus amount needed.
Note the etched number on the face of the drive pin-
ion gear (±1, ±2, 0, +1, +2, etc.). The numbers represent
Fig. 4 PINION GEAR ID NUMBERS
1 - PRODUCTION NUMBERS
2 - PINION GEAR DEPTH VARIANCE
3 - GEAR MATCHING NUMBER
Fig. 5 SHIM LOCATIONS
1 - PINION BEARING PRELOAD SHIM
2 - DIFFERENTIAL BEARING SHIM
3 - PINION GEAR DEPTH SHIM
3 - 112 REAR AXLE - 286RBIBR/BE
REAR AXLE - 286RBI (Continued)

BRAKES - ABS
TABLE OF CONTENTS
page page
BRAKES - ABS
DESCRIPTION.........................35
OPERATION...........................36
DIAGNOSIS AND TESTING - ANTILOCK
BRAKES............................36
STANDARD PROCEDURE
STANDARD PROCEDURE - RWAL SERVICE
PRECAUTIONS.......................36
STANDARD PROCEDURE - BLEEDING ABS
BRAKE SYSTEM......................36
SPECIFICATIONS
TORQUE CHART......................37
FRONT WHEEL SPEED SENSOR
DESCRIPTION.........................38
OPERATION...........................38
REMOVAL
REMOVAL - 4X2......................39REMOVAL - 4X4......................39
INSTALLATION
INSTALLATION - 4X2...................39
INSTALLATION - 4X4...................39
REAR WHEEL SPEED SENSOR
DIAGNOSIS AND TESTING - REAR WHEEL
SPEED SENSOR......................40
REMOVAL.............................40
INSTALLATION.........................40
HCU (HYDRAULIC CONTROL UNIT)
DESCRIPTION.........................40
OPERATION...........................40
REMOVAL.............................41
INSTALLATION.........................41
BRAKES - ABS
DESCRIPTION
The antilock brake system (ABS) is an electroni-
cally operated, all wheel brake control system. 2500
and 3500 vehicles have Electronic Brake Distribution
(EBD) designed into the systen which eliminates the
combination/proportioning valve.
The system is designed to prevent wheel lockup
and maintain steering control during periods of high
wheel slip when braking. Preventing lockup is accom-
plished by modulating fluid pressure to the wheel
brake units.
The hydraulic system is a three channel design.
The front wheel brakes are controlled individually
and the rear wheel brakes in tandem (Fig. 1). The
ABS electrical system is separate from other electri-
cal circuits in the vehicle. A specially programmed
controller antilock brake unit operates the system
components.
ABS system major components include:
²Controller Antilock Brakes (CAB)
²Hydraulic Control Unit (HCU)
²Wheel Speed Sensors (WSS)²ABS Warning Light
Fig. 1 Antilock Brake System
1 - MASTER CYLINDER AND RESERVOIR
2 - POWER BRAKE BOOSTER
3 - WIRES TO WHEEL SPEED SENSORS
4 - RIGHT REAR WHEEL
5 - LEFT REAR WHEEL
6 - HYDRAULIC BRAKE LINES TO WHEELS
7 - COMBINATION VALVE
8 - HARNESS
9 - RIGHT FRONT WHEEL
10 - LEFT FRONT WHEEL
11 - CAB/HCU
BR/BEBRAKES - ABS 5 - 35

OPERATION
Battery voltage is supplied to the CAB when a
speed of 15 miles per hour is reached. The CAB per-
forms a system initialization procedure at this point.
Initialization consists of a static and dynamic self
check of system electrical components.
The static and dynamic checks occurs at ignition
start up. During the dynamic check, the CAB briefly
cycles the pump and solenoids to verify operation. An
audible noise may be heard during this self check.
This noise should be considered normal.
If an ABS component exhibits a fault during ini-
tialization, the CAB illuminates the amber warning
light and registers a fault code in the microprocessor
memory.
The CAB monitors wheel speed sensor inputs con-
tinuously while the vehicle is in motion. However,
the CAB will not activate any ABS components as
long as sensor inputs indicate normal braking.
During normal braking, the master cylinder, power
booster and wheel brake units all function as they
would in a vehicle without ABS. The HCU compo-
nents are not activated.
The purpose of the antilock system is to prevent
wheel lockup during periods of high wheel slip. Pre-
venting lockup helps maintain vehicle braking action
and steering control.
The antilock CAB activates the system whenever
sensor signals indicate periods of wheel slip. Periods
of wheel slip occur when brake stops involve high
pedal pressure and rate of vehicle deceleration.
The antilock system prevents lockup during a
wheel slip condition by modulating fluid apply pres-
sure to the wheel brake units.
Brake fluid apply pressure is modulated according
to wheel speed, degree of slip and rate of decelera-
tion. Sensors at each front wheel convert wheel speed
into electrical signals. These signals are transmitted
to the CAB for processing and determination of
wheel slip and deceleration rate.
The ABS system has three fluid pressure control
channels. The front brakes are controlled separately
and the rear brakes in tandem. A speed sensor input
signal indicating a wheel slip condition activates the
CAB antilock program.
There are Two solenoid valves (Isolation and Dump
valve) which are used in each antilock control chan-
nel. The valves are all located within the HCU valve
body and work in pairs to either increase, hold, or
decrease apply pressure as needed in the individual
control channels.
During an ABS stop the ISO valve actuates, Stop-
ping anymore pressure build Ðup to the calipers.
Then the Dump valve dumps off pressure until the
wheel unlocks. This will continue until the wheels
quit slipping altogether.
DIAGNOSIS AND TESTING - ANTILOCK
BRAKES
The ABS brake system performs several self-tests
every time the ignition switch is turned on and the
vehicle is driven. The CAB monitors the systems
input and output circuits to verify the system is oper-
ating correctly. If the on board diagnostic system
senses that a circuit is malfunctioning the system
will set a trouble code in its memory.
NOTE: An audible noise may be heard during the
self-test. This noise should be considered normal.
NOTE: The MDS or DRB III scan tool is used to
diagnose the ABS system. For additional informa-
tion refer to the Antilock Brake section in Group
8W. For test procedures refer to the Chassis Diag-
nostic Manual.
STANDARD PROCEDURE
STANDARD PROCEDURE - RWAL SERVICE
PRECAUTIONS
The RWAL uses an electronic control module, the
CAB. This module is designed to withstand normal
current draws associated with vehicle operation.
Care must be taken to avoid overloading the CAB
circuits.In testing for open or short circuits, do
not ground or apply voltage to any of the cir-
cuits unless instructed to do so for a diagnostic
procedure.These circuits should only be tested
using a high impedance multi-meter or the DRB
tester as described in this section. Power should
never be removed or applied to any control module
with the ignition in the ON position. Before removing
or connecting battery cables, fuses, or connectors,
always turn the ignition to the OFF position.
CAUTION: Use only factory wiring harnesses. Do
not cut or splice wiring to the brake circuits. The
addition of after-market electrical equipment (car
phone, radar detector, citizen band radio, trailer
lighting, trailer brakes, ect.) on a vehicle equipped
with antilock brakes may affect the function of the
antilock brake system.
STANDARD PROCEDURE - BLEEDING ABS
BRAKE SYSTEM
ABS system bleeding requires conventional bleed-
ing methods plus use of the DRB scan tool. The pro-
cedure involves performing a base brake bleeding,
followed by use of the scan tool to cycle and bleed the
5 - 36 BRAKES - ABSBR/BE
BRAKES - ABS (Continued)

HCU pump and solenoids. A second base brake bleed-
ing procedure is then required to remove any air
remaining in the system.
(1) Perform the base brake bleeding, (Refer to 5 -
BRAKES/HYDRAULIC/MECHANICAL - STAN-
DARD PROCEDURE).
(2) Connect the scan tool to the Data Link Connec-
tor.(3) Select ANTILOCK BRAKES, followed by MIS-
CELLANEOUS, then ABS BRAKES. Follow the
instructions displayed. When scan tool displays TEST
COMPLETE, disconnect scan tool and proceed.
(4) Perform base brake bleeding a second time,
(Refer to 5 - BRAKES/HYDRAULIC/MECHANICAL -
STANDARD PROCEDURE).
(5) Top off master cylinder fluid level and verify
proper brake operation before moving vehicle.
SPECIFICATIONS
TORQUE CHART
TORQUE SPECIFICATIONS
DESCRIPTION N´m Ft. Lbs. In. Lbs.
ABS Assembly
Bracket Bolts13 10 120
ABS Assembly
Mounting Nuts13 10 102
ABS Assembly
CAB Screws4335
ABS Assembly
Brake Lines21 15 190
Wheel Speed Sensor
Frt. Bolts (4x2)23 17 200
Wheel Speed Sensor
Frt. Bolts (4x4)14 10 120
Wheel Speed Sensor
Rear Bolt24 18 210
BR/BEBRAKES - ABS 5 - 37
BRAKES - ABS (Continued)

FRONT WHEEL SPEED
SENSOR
DESCRIPTION
The ABS brake system uses 3 wheel speed sensors.
A sensor is mounted to each front steering knuckles.
The third sensor is mounted on top of the rear axle
differential housing.
OPERATION
The Wheel Speed Sensor consists of a magnet sur-
rounded by windings from a single strand of wire.
The sensor sends a small AC signal to the CAB. This
signal is generated by magnetic induction. The mag-
netic induction is created when a toothed sensor ring
(exciter ring or tone wheel) passes the stationary
magnetic WSS.
When the ring gear is rotated, the exciter ring
passes the tip of the WSS. As the exciter ring tooth
approaches the tip of the WSS, the magnetic lines of
force expand, causing the magnetic field to cut across
the sensor's windings. This, in turn causes current to
flow through the WSS circuit (Fig. 2) in one direc-
tion. When the exciter ring tooth moves away from
the sensor tip, the magnetic lines of force collapse
cutting the winding in the opposite direction. This
causes the current to flow in the opposite direction.
Every time a tooth of the exciter ring passes the tip
of the WSS, an AC signal is generated. Each AC sig-
nal (positive to negative signal or sinewave) is inter-
preted by the CAB. It then compares the frequency of
the sinewave to a time value to calculate vehicle
speed. The CAB continues to monitor the frequency
to determine a deceleration rate that would indicate
a possible wheel-locking tendency.
The signal strength of any magnetic induction sen-
sor is directly affected by:
²Magnetic field strength; the stronger the mag-
netic field, the stronger the signal
²Number of windings in the sensor; more wind-
ings provide a stronger signal
²Exciter ring speed; the faster the exciter ring/
tone wheel rotates, the stronger the signal will be
²Distance between the exciter ring teeth and
WSS; the closer the WSS is to the exciter ring/tone
wheel, the stronger the signal will be
The rear WSS is not adjustable. A clearance speci-
fication has been established for manufacturing toler-
ances. If the clearance is not within these
specifications, then either the WSS or other compo-
nents may be damaged. The clearance between the
WSS and the exciter ring is 0.005 ± 0.050 in.
The assembly plant performs a ªRolls Testº on
every vehicle that leaves the assembly plant. One of
the test performed is a test of the WSS. To properlytest the sensor, the assembly plant connects test
equipment to the Data Link Connector (DLC). This
connector is located to the right of the steering col-
umn and attached to the lower portion of the instru-
ment panel (Fig. 3). The rolls test terminal is spliced
to the WSS circuit. The vehicle is then driven on a
set of rollers and the WSS output is monitored for
proper operation.
Fig. 2 Operation of the Wheel Speed Sensor
1 - MAGNETIC CORE
2 - CAB
3 - AIR GAP
4 - EXCITER RING
5 - COIL
Fig. 3 Data Link Connector - Typical
1 - 16±WAY DATA LINK CONNECTOR
5 - 38 BRAKES - ABSBR/BE

REMOVAL
REMOVAL - 4X2
(1) Raise and support vehicle.
(2) Disconnect the ABS wheel speed sensor wire
from under the hood. Remove sensor wire from the
frame, brake hose and steering knuckle.
(3) Remove sensor bolt from the backside of the
steering knuckle and remove the sensor (Fig. 4).
REMOVAL - 4X4
(1) Disconnect the ABS wheel speed sensor wire
from under the hood.
(2) Raise and support the vehicle.
(3) Remove the tire and wheel assembly.
(4) Remove the sensor wire from the clips on the
brake hose.
(5) Remove the brake caliper. (Refer to 5 -
BRAKES/HYDRAULIC/MECHANICAL/DISC
BRAKE CALIPERS - REMOVAL).
(6) Remove the disc brake rotor and adapter.
(Refer to 5 - BRAKES/HYDRAULIC/MECHANICAL/
ROTORS - REMOVAL).
(7) Bend the tab on the dust shield upwards to
allow access to the bolt.
(8) Remove the bolt attaching the sensor to the
hub bearing. (Fig. 5)
(9) Remove the sensor wire.
INSTALLATION
INSTALLATION - 4X2
(1) Position sensor in knuckle.
(2) Install and tighten sensor bolt to 23 N´m (17 ft.
lbs.).Use original or replacement sensor bolt
only. The bolt is special and must not be substi-
tuted.
(3) Install sensor wire to the steering knuckle,
brake hose and frame. Connect the wheel speed sen-
sor wire under the hood.
(4) Check sensor wire routing. Be sure wire is
clear of all chassis components and is not twisted or
kinked at any spot.
(5) Remove support and lower the vehicle.
(6) Verify sensor operation with scan tool.
INSTALLATION - 4X4
NOTE: Use original or replacement sensor bolts
only. The bolts are special and must not be substi-
tuted.
(1) Install the sensor in the hub bearing and
tighten the bolt to 14 N´m (11 ft. lbs.). (Fig. 5)
(2) Bend the dust shield tab back downwards into
position.
(3) Install the disc brake rotor and caliper adapter.
(Refer to 5 - BRAKES/HYDRAULIC/MECHANICAL/
ROTORS - REMOVAL).
(4) Install the brake caliper. (Refer to 5 - BRAKES/
HYDRAULIC/MECHANICAL/DISC BRAKE CALI-
PERS - REMOVAL).
(5) Route the wire into the clips.
Fig. 4 Wheel Speed Sensor - 4x2
1 - KNUCKLE
2 - SENSOR
Fig. 5 WHEEL SPEED SENSOR - 4X4
1 - HUB/BEARING
2 - WHEEL SPEED SENSOR
BR/BEBRAKES - ABS 5 - 39