Jeep 1997 Grand Cherokee Service Manual page 146

DIFFERENTIAL SHIM-PINION GEAR SIDE BEARING
PINION GEAR DEPTH SHIM
3 - 88 DIFFERENTIAL AND DRIVELINE
GENERAL INFORMATION (Continued)
Fig. 1 Shim Locations
RBA axle lubricant capacity is 2.25 L (4.75 pts.) total,
including the friction modifier if necessary.
CAUTION: If axle is submerged in water, lubricant
must be replaced immediately to avoid possible
premature axle failure.
DESCRIPTION AND OPERATION
STANDARD DIFFERENTIAL
The differential gear system divides the torque
between the axle shafts. It allows the axle shafts to
rotate at different speeds when turning corners.
Each differential side gear is splined to an axle
shaft. The pinion gears are mounted on a pinion
mate shaft and are free to rotate on the shaft. The
pinion gear is fitted in a bore in the differential case
and is positioned at a right angle to the axle shafts.
In operation, power flow occurs as follows:
• The pinion gear rotates the ring gear
• The ring gear (bolted to the differential case)
rotates the case
• The differential pinion gears (mounted on the
pinion mate shaft in the case) rotate the side gears
• The side gears (splined to the axle shafts) rotate
the shafts
During straight-ahead driving, the differential pin-
ion gears do not rotate on the pinion mate shaft. This
occurs because input torque applied to the gears is
divided and distributed equally between the two side
gears. As a result, the pinion gears revolve with the
pinion mate shaft but do not rotate around it (Fig. 1).
When turning corners, the outside wheel must
travel a greater distance than the inside wheel to
complete a turn. The difference must be compensated
for to prevent the tires from scuffing and skidding
through turns. To accomplish this, the differential
allows the axle shafts to turn at unequal speeds (Fig.
PINION GEARS ROTATE ON IN STRAIGHT AHEAD DRIVING EACH WHEEL ROTATES AT 100% OF CASE PINION GEARS ROTATE WITH PINION SHAFT 100%
OUTER WHEEL 110% CASE
SPEED
Fig. 2 Differential Operation—StraightAhead Driving
2). In this instance, the input torque applied to the
pinion gears is not divided equally. The pinion gears
now rotate around the pinion mate shaft in opposite
directions. This allows the side gear and axle shaft
attached to the outside wheel to rotate at a faster
speed.
Fig. 3 Differential Operation—On Turns
TRAC-LOK OPERATION
In a conventional differential, if one wheel spins,
the opposite wheel will generate only as much torque
as the spinning wheel.
In the Trac-lok differential, part of the ring gear
torque is transmitted through clutch packs which
contain multiple discs. The clutches will have radial
grooves on the plates, and concentric grooves on the
discs or bonded fiber material that is smooth in
appearance.
In operation, the Trac-lok clutches are engaged by
two concurrent forces. The first being the preload
force exerted through Belleville spring washers
within the clutch packs. The second is the separating
forces generated by the side gears as torque is
applied through the ring gear (Fig. 4).
PINION GEAR AXLE DIFFERENTIAL CASE SPEED CASE SPEED SIDE GEAR
INNER WHEEL 90% CASE
SPEED
ZG