Jeep 1996 Grand Cherokee Service Manual - page 1489
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 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.
TRAC–LOK DIFFERENTIAL NOISE
The most common problem is a chatter noise when
turning corners. Before removing a Trac-lok unit for
repair, drain, flush and refill the axle with the spec-
ified lubricant. Refer to Lubricant change in this
Group.
A container of Mopar
t Trac-lok Lubricant (friction
modifier) should be added after repair service or a
lubricant change.
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. This
will correct the condition in most instances. If the
chatter persists, clutch damage could have occurred.
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DIFFERENTIAL AND DRIVELINE
ZJ
DIAGNOSIS AND TESTING (Continued)