Jeep 1996 Grand Cherokee Service Manual page 92

ZJ
DIAGNOSIS AND TESTING (Continued)
• Damaged axle shaft bearings
• Loose pinion gear nut
• Excessive pinion yoke run out
• Bent axle shaft
Check for loose or damaged front–end components
or engine/transmission mounts. These components
can contribute to what appears to be a rear–end
vibration. Do not overlook engine accessories, brack-
ets and drive belts.
All driveline components should be examined
before starting any repair.
Refer to Group 22, Wheels and Tires for additional
information.
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
• 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/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.
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-
DIFFERENTIAL AND DRIVELINE
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
in. (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 mea-
surements. 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 mea-
surement, 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.
LIMITED SLIP DIFFERENTIAL
Under normal traction conditions, engine torque is
divided evenly. With low–traction surfaces, engine
torque is transferred to the wheel with the most tire
traction. When diagnosing a limited–slip differential
the wheel with the least traction can continue spin-
ning.
The most common problem is a chatter noise when
turning corners. Check for incorrect or contaminated
lubricant. Replace the gear lubricant if necessary.
• With Trac–Lok
Mopar Trac–Lok Lubricant.
This will correct the condition in most instances. If
the chatter persists, clutch damage could have
occurred.
After changing the lubricant, drive the vehicle and
make 10 to 12 slow, figure–eight turns. This maneu-
ver will pump lubricant through the clutches.
differentials add a container of
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