Jeep Grand Cherokee WJ. Manual - part 704

range. The noise can also occur during a specific type
of driving condition. These conditions are accelera-
tion, deceleration, coast, or constant load.

When road testing, first warm-up the axle fluid by

driving the vehicle at least 5 miles and then acceler-
ate 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 insufficient lubricant.

• Incorrect ring gear backlash.

• Gear damage.
Differential side gears and pinions can be checked

by turning the vehicle. They usually do not cause
noise during straight-ahead driving when the gears
are unloaded. The side gears are loaded during vehi-
cle turns. A worn pinion mate shaft can also cause a
snapping or a knocking noise.

BEARING NOISE

The axle shaft, differential and pinion bearings can

all produce noise when worn or damaged. Bearing
noise can be either a whining, or a growling sound.

Pinion bearings have a constant-pitch noise. This

noise changes only with vehicle speed. Pinion bearing
noise will be higher pitched because it rotates at a
faster rate. Drive the vehicle and load the differen-

tial. If bearing noise occurs, the rear pinion bearing
is the source of the noise. If the bearing noise is
heard during a coast, the front pinion bearing is the
source.

Worn or damaged differential bearings usually pro-

duce a low pitch noise. Differential bearing noise is
similar to pinion bearing noise. The pitch of differen-
tial 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
level. Where axle bearing damage is slight, the noise
is usually not noticeable at speeds above 30 mph.

LOW SPEED KNOCK

Low speed knock is generally caused by a worn

U-joint or by worn side–gear thrust washers. A worn
pinion shaft bore will also cause low speed knock.

VIBRATION

Vibration at the rear of the vehicle is usually

caused by a:

• Damaged drive shaft.

• Missing drive shaft balance weight(s).

• Worn or out-of-balance wheels.

• Loose wheel lug nuts.

• Worn U-joint(s).

• Loose/broken springs.

• Damaged axle shaft bearing(s).

• Loose pinion gear nut.

• Excessive pinion yoke run out.

• Bent axle shaft(s).
Check for loose or damaged front-end components

or engine/transmission mounts. These components
can contribute to what appears to be a rearend vibra-

REAR AXLE - 198RBI

3s - 17

2001 JEEP GRAND CHEROKEE

tion. Do not overlook engine accessories, brackets
and drive belts.

All driveline components should be examined

before starting any repair.

(Refer to 22 - TIRES/WHEELS - DIAGNOSIS AND

TESTING)

DRIVELINE SNAP

A snap or clunk noise when the vehicle is shifted

into gear (or the clutch engaged), can be caused by:

• High engine idle speed.

• Transmission shift operation.

• Loose engine/transmission/transfer case mounts.

• Worn U-joints.

• Loose spring mounts.

• Loose pinion gear nut and yoke.

• Excessive ring gear backlash.

• Excessive side gear to case clearance.
The source of a snap or a clunk noise can be deter-

mined with the assistance of a helper. Raise the vehi-
cle on a hoist with the wheels free to rotate. Instruct
the helper to shift the transmission into gear. Listen
for the noise, a mechanics stethoscope is helpful in
isolating the source of a noise.

DIAGNOSTIC CHART

Condition

Possible Causes

Correction

Wheel Noise

1. Wheel loose.

1. Tighten loose nuts.

2. Faulty, brinelled wheel bearing.

2. Replace bearing.

Axle Shaft Noise

1. Misaligned axle tube.

1. Inspect axle tube alignment. Correct
as necessary.

2. Bent or sprung axle shaft.

2. Inspect and correct as necessary.

3. End-play in pinion bearings.

3. Refer to pinion pre-load information
and correct as necessary.

4. Excessive gear backlash between the
ring gear and pinion.

4. Check adjustment of the ring gear and
pinion backlash. Correct as necessary.

5. Improper adjustment of pinion gear
bearings.

5. Adjust the pinion bearings pre-load.

6. Loose pinion yoke nut.

6. Tighten the pinion yoke nut.

7. Scuffed gear tooth contact surfaces.

7. Inspect and replace as necessary.

Axle Shaft Broke

1. Misaligned axle tube.

1. Replace the broken shaft after
correcting tube mis-alignment.

2 Vehicle overloaded.

2. Replace broken shaft and avoid
excessive weight on vehicle.

3. Erratic clutch operation.

3. Replace broken shaft and avoid or
correct erratic clutch operation.

4. Grabbing clutch.

4. Replace broken shaft and inspect and
repair clutch as necessary.

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2001 JEEP GRAND CHEROKEE

Condition

Possible Causes

Correction

Differential Cracked

1. Improper adjustment of the differential
bearings.

1. Replace case and inspect gears and
bearings for further damage. Set
differential bearing pre-load properly.

2. Excessive ring gear backlash.

2. Replace case and inspect gears and
bearings for further damage. Set ring
gear backlash properly.

3. Vehicle overloaded.

3. Replace case and inspect gears and
bearings for further damage. Avoid
excessive vehicle weight.

4. Erratic clutch operation.

4. Replace case and inspect gears and
bearings for further damage. Avoid
erratic use of clutch.

Differential Gears Scored

1. Insufficient lubrication.

1. Replace scored gears. Fill differential
with the correct fluid type and quantity.

2. Improper grade of lubricant.

2. Replace scored gears. Fill differential
with the correct fluid type and quantity.

3. Excessive spinning of one wheel/tire.

3. Replace scored gears. Inspect all
gears, pinion bores, and shaft for
damage. Service as necessary.

Loss Of Lubricant

1. Lubricant level too high.

1. Drain lubricant to the correct level.

2. Worn axle shaft seals.

2. Replace seals.

3. Cracked differential housing.

3. Repair as necessary.

4. Worn pinion seal.

4. Replace seal.

5. Worn/scored yoke.

5. Replace yoke and seal.

6. Axle cover not properly sealed.

6. Remove, clean, and re-seal cover.

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.

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2001 JEEP GRAND CHEROKEE

Condition

Possible Causes

Correction

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.

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.

ADJUSTMENTS

PINION GEAR DEPTH

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.
1). 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 96.850 mm (3.813 in.). The standard depth pro-
vides the best gear tooth contact pattern. Refer to
Backlash and Contact Pattern Analysis paragraph in
this section for additional information.

Compensation

for

pinion

depth

variance

achieved with a select shim/oil baffle. The shims are
placed between the rear pinion bearing and the pin-
ion gear head (Fig. 2).

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 Pinion Gear Depth Variance chart.

Note where Old and New Pinion Marking columns

intersect.

Intersecting

figure

represents

plus

minus the amount needed.

Fig. 1 Pinion Gear ID Numbers

1 - PRODUCTION NUMBERS
2 - PINION GEAR DEPTH VARIANCE
3 - GEAR MATCHING NUMBER)

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2001 JEEP GRAND CHEROKEE

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