GMC 1990 Light Truck Repair Manual page 142

4B1-8 71/z AND 7%-INCH RING GEAR AXLES
4.32 MM (0.170-INCH) SERVICE SPACER
Total Thickness of
Both Prod. Shims
Removed
10.57 mm (0.420-inch)
10.92 mm (0.430-inch)
11.18 mm (0.440-inch)
11.43 mm (0.450-inch)
11.68 mm (0.460-inch)
11.94 mm (0.470-inch)
12.19 mm (0.480-inch)
12.45 mm (0.490-inch)
12.70 mm (0.500-inch)
12.95 mm (0.510-inch)
13.21 mm (0.520-inch)
13.46 mm (0.530-inch)
13.97 mm (0.550-inch)
Figure 13—Shim Thickness Chart
5. Install the shim(s) between the right bearing cup
and the service shim.
• The left bearing race and spacer must be against
the left side of the housing.
6. D eterm ine bearing
progressively larger feeler gage sizes between the
right service spacer and shim.
• Push the feeler gage downward so that it
contacts the shim at the top and bottom, and
then contacts the axle housing.
• Rotate the case while using the feeler gage.
This will assure an accurate reading.
• The weight of the case will cause a light drag.
Do not mistake this drag for bearing preload.
• Start with a thin feeler gage to obtain a feel for
when preload begins. It will be necessary to
work the case in or out and to the left in order
to insert the feeler gage.
• The point just before additional drag begins is
the correct feeler gage thickness. This is the
zero setting without pre-load.
7. Remove the left bearing cap and shim(s) from the
axle housing. M easure the shim s using a
micrometer. The shim pack needed is the total of the
shim(s) and the feeler gage. An additional pre-load
of 0.10 mm (0.004-inch) will be added to each side of
the differential case after the backlash adjustment is
made.
8. Differential case, bearing cups, shims and spacers.
9. Install the pinion. Refer to " Pinion Installation" in
this section.
PINION INSTALLATION
+ 4- Install or Connect
Tools Required:
J 5590 Rear Pinion Bearing Cone Installer
J 23911 Pinion Oil Seal Installer
J 8614-01 Pinion Flange Remover
The bearing cups should have been installed in
" Pinion Depth Adjustment," in this section.
The pinion inner bearing (18) using J 5590 (figure
14).
Total Thickness of
Service Shims To Be
Used As A Starting Point
1.52 mm (0.060-inch)
1.78 mm (0.070-inch)
2.03 mm (0.080-inch)
2.29 mm (0.090-inch)
2.54 mm (0.100-inch)
2.79 mm (0.110-inch)
3.05 mm (0.120-inch)
3.30 mm (0.130-inch)
3.56 mm (0.140-inch)
3.81 mm (0.150-inch)
4.06 mm (0.160-inch)
4.32 mm (0 170-inch)
4.83 mm (0.190-inch)
F -0 4 6 8 5
pre-load by in se rtin g
Figure 14—Installing the Pinion Inner Bearing
• Drive the bearing until the bearing cone seats
on the pinion shims.
2 A new collapsible spacer (17).
• Lubricate the pinion bearings with axle lubricant.
3. Pinion (20) to the axle housing.
4. Outer pinion bearing (15) onto the pinion using
J 5590.
• Hold the pinion forward from inside the case
while driving the bearing onto the pinion.
5. Pinion oil seal (14) using J 23911.
6. The pinion flange (13) to the pinion by tapping it with
a rawhide hammer until a few threads show through
the pinion flange.
7. The pinion washer (12) and a new nut (11) while
holding the pinion flange with J 8614-01.
Tighten
The nut until the pinion end play is just taken
up. Rotate the pinion while tightening the nut
to seat the bearings. Once there is no end play
in the pinion, the preload torque should be
checked.
Remove J 8614-01. Using an inch-pound
torque wrench, check the pinion preload by
rotating the pinion with the wrench (figure 15).