GMC 1982 Light Duty Truck, Service Manual

Page: 436 / 1435

4 B 1 - 8 R EA R A X L E
Fig. 4B1 -21 -Installing Gaging Tool
housing as shown in figure 4 B 1 -21.
5. While oscillating tool, turn adjusting nut clockwise
until a noticeable drag is produced.
6. Tighten lock bolt on side of tool.
7. Between the right bearing and carrier, install Service
Spacer A (.1 7 0 " ), Service Shim B and Feeler Gage C.
Thickness of Feeler G age must be sufficient to produce
a slight " d r a g " when moved betw een c a rrie r and
Service Shim.
8. Now measure the above dimensions as shown in figure
4B1-22.
a. Using a micrometer as in figure 4B1-23, measure the
thickness of J-22779 in a minim um of three places
and average these readings. Record the result.
b. Add together the dimensions of the Service Shim,
Service Spacer and Feeler Gage. Record the result.
9. Use th e sam ple pro ced u re in figure 4B1-22 to
determine the proper thickness for each shim pack.
NOTICE: Production preloading of th e differential
bearings is accomplished by the use of cast iron preload
shim. These shims cannot be used when rebuilding the
carrier as they may break when tapped into place.
10. Install left shim first, then wedge right shim between
bearing cup and spacer. Position shim so t h a t
chamfered side is outward or next to spacer. If shim
does not have sufficient cham fer or lead around O.D. to
allow easy installation without scraping spacer, file or
grind chamfer before installing.
11. If difficulty is encountered in installing shim, partially
remove case and slide case and shim into position. Tap
shim into position, using a soft faced ham m er, while
rotating differential case with free hand as shown in
figure 4B1-24.
12. Install bearing caps in original position and torque to
80 N-m (60 ft. lbs.).
At this point, the differential side bearings are properly
preloaded. If any adjustments are required in later
procedures, m ake sure the preload rem ains as
established in step 9. If backlash is changed in later
steps, be sure the
total thickness of the two shim packs
does not change.
13. Mount a dial indicator on the carrier and check the
backlash between the ring gear and pinion, as shown in
figure 4B1-25. The backlash should be within the range
of 0.0 0 5 "-0 .0 0 8 " . Check gear lash at four different
equally spaced positions around the gear. Variation in
readings should not exceed .001". Position the dial
indicator so that indicator button is perpendicular to
tooth angle and in line with gear rotation.
14. If variation in backlash readings exceeds .0 0 2 " ;
measure ring gear and case runout as shown in figure
4B1-26. Gear runout should not exceed .0 03"; should
runout exceed this limit, check ring gear and case for
deformation a n d /o r foreign m atter between case and
gear.
15. If gear lash is not within limits, correct by decreasing
shim thickness on one side and increasing thickness of
other shim
the same amount. Total shim thickness must
be maintained at all times to maintain proper preload.
16. Backlash changes approximately .002" for each .003"
change in shim dimensions.
• I f backlash exceeds .008 ", increase the shim thickness
on the ring gear side, while d ecreasing the shim
thickness on the opposite side
an equal amount.
• I f b acklash is less than .005", d e c re a se the shim
thickness on the ring gear side, while increasing the
shim th ickness on the opposite side an equal amount.
D iffe re n tia l Backlash A d ju s tm e n t (9 1 I I " Ring G ear)
1. Place bearing cups over side bearings and lift the
differential assembly into the carrier.
2. Install bearing shim.
3. Push case towards bearing shim side of carrier.
4. Tighten adjusting nut using tool J-24429 and rotate
pinion to seat bearings as shown in Fig. 4 B 1 -27.
5. Back adjusting nut off and install bearing cups loosely.
6. Turn adjusting nut until initial contact and index 3
additional slots.
7. Install bearing caps to 80 N-m (70 ft. lbs.).
8. Install locking retainers into holes and attach fingers to
bearing cap loosely.
9. At this time, the differential bearings are properly
preloaded. If any additional adjustm ent is required,
make sure th at the preload remains established.
10. M ount a dial indicator on the housing and measure
backlash between the ring gear and pinion. Backlash
should be .075 mm - .25 mm (.003 - .010) with .125 mm
- .20 mm (.005 - .008) preferred.
11. If reading is too high, increase bearing shim size. If
reading is too low, decrease bearing shim size.
12. Torque locking retainer to 30 N-m (20 ft. lbs.).
A service spacer 4.34 mm (.171) thick is available.
Service shims are available from 1.278 - 2.256 mm
(0.50 - .088) in increments of .050 mm (.002).
Pinion shims are available from .5080 - .9398 mm (.020
- .037) in increments of .025 mm (.001).