GMC 1982 Light Duty Truck, Service Manual

Page: 460 / 1435

4 B 3 - 6 R EAR A X L E
J-8 6 1 4 -1 1, torque nut to 350 N-m (250 lbs. ft.).
DIFFERENTIAL CASE
In s ta lla tio n a n d A d ju s tm e n t
1. Place the differential case, with side bearings and cups
installed, into position in the carrier.
2. Select the smallest of the original shims as a “gaging'’
shim and place it betw een the bearing cup and the
carrier on the ring gear side of the case.
3. Install bearing caps and bearing screws finger tight.
Make sure bearing caps are in correct marked position.
4. Mount a dial indicator on the ring gear side of the
carrier, with the indicator probe in contact with the
back face of the ring gear.
5. Position two screwdrivers between the bearing cup and
the carrier on the side opposite the ring gear.
6. Pull on the screwdrivers and force the differential case
as far as possible toward the indicator. With force still
applied, set the dial indicator to zero.
7. Reposition the screwdrivers on the ring gear side of the
case. Force the ring gear into mesh with the drive
pinion and observe the dial indicator. R e p e a t this
operatio several times until the sam e reading is
obtained.
8. A dd the indicator read in g to the ‘g a g in g 1 shim
thickness to determine the correct shim dimension for
installation on the ring gear side of the case.
For example, if the gaging shim was .155 inch, and the
indicator reading in step 7 was .017 inch, the correct
shim would be .155 + .017 = .172 inch.
9. R em ove the “gaging” shim and install the correct size
shim into position b etw een the bearing cup and the
carrier on the ring gear side of the case.
10. To determine the correct dimension for the remaining
shim, first refer to the dimension obtained in step 8 of
“ Gaging Procedures and Side Bearing S h im s” . From
that figure, subtract the size of the shim installed in
step 9 above; then add .006 inch for preload and
backlash.
For example, if the reading in step 8 was .329 inch, and
the shim just installed on the ring gear side of the case
was .172 inch, the correct shim dimension would be
.329-.172 = .157 + .006 = .163 inch.
11. Spread the differential carrier as shown in figure 4B3-
2 .
12. Assemble the shim determined in step 10 into place
between the bearing cup and the carrier.
13. Remove the spreader and the dial indicator.
14. Install the bearing caps in marked positions and torque
cap screws to specifications.
15. Install dial indicator and check ring gear backlash at
four equally spaced points aro u n d the ring gear.
Backlash must be held to .004‘ to .009‘ and must not
vary more than ,002‘ between positions checked.
16. Whenever backlash is not within limits, differential
bearing shim pack should be corrected to bring
backlash within limits.
• Low backlash is corrected by decreasing the shim on
the ring gear side and increasing the opposite side
shim
an equal amount.
• High backlash is corrected by increasing the shim on
the ring gear side and decreasing the opposite side
shim
an equal amount.
17. Check gear tooth contact, as described in ‘Gear Tooth
Contact Pattern C heck‘.
18. Using a new gasket, install housing cover and torque
bolts to specifications.
19. Reinstall the rear universal joint, and torque ‘U ‘ bolt
nuts to specifications.
20. Install axles into carrier and axle flange over hub studs.
21. Torque hub stud nuts to specifications.
22. Fill differential with lubricant.
23. Install wheel and tire assembly.
O PER A TIO N A L CHECKS A N D AD JU STM ENTS
Four adjustm ents are essential for proper operation of
the differential and its related parts. These adjustments are
a) Pinion Bearing Preload, b) Side Bearing Preload, c)
Pinion Depth and d) Ring Gear-to-Pinion Backlash.
Refer to Section 4B for description of how to perform
these checks and adjustments.