Jeep 1997 Grand Cherokee Service Manual page 110

CLUTCH PACK CASE RING GEAR
3 - 52 DIFFERENTIAL AND DRIVELINE
DESCRIPTION AND OPERATION (Continued)
Fig. 4 Trac-lok Limited Slip DifferentialOperation
The Trac-lok design provides the differential action
needed for turning corners and for driving straight
ahead during periods of unequal traction. When one
wheel looses traction, the clutch packs transfer addi-
tional torque to the wheel having the most traction.
Trac-lok differentials resist wheel spin on bumpy
roads and provide more pulling power when one
wheel looses traction. Pulling power is provided con-
tinuously until both wheels loose traction. If both
wheels slip due to unequal traction, Trac-lok opera-
tion is normal. In extreme cases of differences of
traction, the wheel with the least traction may spin.
DIAGNOSIS AND TESTING
GENERAL INFORMATION
Axle bearing problem conditions are usually caused
by:
• Insufficient or incorrect lubricant.
• Foreign matter/water contamination.
• Incorrect bearing preload torque adjustment.
• Incorrect backlash.
Axle gear problem conditions are usually the result
of:
• Insufficient lubrication.
• Incorrect or contaminated lubricant.
SIDE GEAR PINION GEAR DRIVE PINION CLUTCH PACK MATE SHAFT
• Overloading (excessive engine torque) or exceed-
ing vehicle weight capacity.
• Incorrect clearance or backlash adjustment.
Axle component breakage is most often the result
of:
• Severe overloading.
• Insufficient lubricant.
• Incorrect lubricant.
• Improperly tightened components.
GEAR NOISE
Axle gear noise can be caused by insufficient lubri-
cant, incorrect backlash, tooth contact, or worn/dam-
aged gears.
Gear noise usually happens at a specific speed
range. The range is 30 to 40 mph, or above 50 mph.
The noise can also occur during a specific type of
driving condition. These conditions are acceleration,
deceleration, coast, or constant load.
When road testing, accelerate 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 and pinion gears 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 gear mate shaft can also
cause a snapping or a knocking noise.
BEARING NOISE
The axle shaft, differential and pinion gear bear-
ings can all produce noise when worn or damaged.
Bearing noise can be either a whining, or a growling
sound.
Pinion gear bearings have a constant–pitch noise.
This noise changes only with vehicle speed. Pinion
bearing noise will be higher 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
ZG