Gear Contact Pattern Analysis - Jeep cherokee 2000 Service Manual

XJ
ADJUSTMENTS (Continued)
(25) Subtract 0.002 in. (0.05 mm) from the dial
indicator reading to compensate for backlash between
ring and pinion gears. This total is the thickness
shim required to achieve proper backlash.
(26) Subtract the backlash shim thickness from
the total preload shim thickness. The remainder is
the shim thickness required on the pinion side of the
axle housing.
(27) Rotate dial indicator out of the way on guide
stud.
(28) Remove differential case and dummy bearings
from axle housing.
(29) Install side bearing shims on differential case
hubs.
(30) Install side bearings and cups on differential
case.
(31) Install spreader W-129-B, utilizing some items
from Adapter Set 6987, on axle housing and spread
axle opening enough to receive differential case.
(32) Install differential case in axle housing.
(33) Remove spreader from axle housing.
(34) Rotate the differential case several times to
seat the side bearings.
(35) Position the indicator plunger against a ring
gear tooth (Fig. 103).
(36) Push and hold ring gear upward while not
allowing the pinion gear to rotate.
(37) Zero dial indicator face to pointer.
(38) Push and hold ring gear downward while not
allowing the pinion gear to rotate. Dial indicator
reading should be between 0.12 mm (0.005 in.) and
0.20 mm (0.008 in.). If backlash is not within specifi-
cations transfer the necessary amount of shim thick-
ness from one side of the axle housing to the other
(Fig. 104).
(39) Verify differential case and ring gear runout
by measuring ring to pinion gear backlash at eight
locations around the ring gear. Readings should not
vary more than 0.05 mm (0.002 in.). If readings vary
more than specified, the ring gear or the differential
case is defective.
After the proper backlash is achieved, perform
Gear Contact Pattern Analysis procedure.

GEAR CONTACT PATTERN ANALYSIS

The ring gear and pinion teeth contact patterns
will show if the pinion depth is correct in the axle
housing. It will also show if the ring gear backlash
has been adjusted correctly. The backlash can be
adjusted within specifications to achieve desired
tooth contact patterns.
(1) Apply a thin coat of hydrated ferric oxide, or
equivalent, to the drive and coast side of the ring
gear teeth.
(2) Wrap, twist, and hold a shop towel around the
pinion yoke to increase the turning resistance of the
TUBE, 181, AND 186 FBI AXLE
Fig. 103 Ring Gear Backlash Measurement
1 – DIAL INDICATOR
Fig. 104 Backlash Shim Adjustment
pinion. This will provide a more distinct contact pat-
tern.
(3) Using a boxed end wrench on a ring gear bolt,
Rotate the differential case one complete revolution
in both directions while a load is being applied from
shop towel.
The areas on the ring gear teeth with the greatest
degree of contact against the pinion teeth will squee-
gee the compound to the areas with the least amount
of contact. Note and compare patterns on the ring
gear teeth to Gear Tooth Contact Patterns chart (Fig.
105) and adjust pinion depth and gear backlash as
necessary.
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