GMC 1990 Light Truck Repair Manual page 169

8. Differential case (27) to the axle housing. Refer to
" Side Bearing Preload Adjustment" in this section.
SIDE BEARING PRELOAD ADJUSTMENT
• The differential side bearing preload is adjusted by
an adjusting nut in the differential bearing bore. The
bore and the bearing cap provide the mating
threads for the bearing nut.
• The differential must be initially preloaded in order
to determine the backlash of the gear set. After the
backlash has been set, the final bearing preload is
set.
Install or Connect
Tool Required:
J 24429 Side Bearing Backlash Spanner
Wrench
The bearing cups (22) to the differential bearings in
their original locations.
Differential assembly to the axle housing.
Bearing shims (21).
Push the case away from the pinion towards the
axle housing.
4. Adjusting nut (17).
Tighten the adjusting nut using J 24429.
Turn the pinion to seat the bearings.
Back off the adjusting nut.
5. Bearing caps (19) and bolts (20) in their original
positions.
• Assemble the caps loosely.
Turn the adjusting nut until the nut contacts the
shim. Then tighten the nut three additional slots
(figure 21).
• The bearing cap bolts to 80 N-m (60 ft. lbs.).
Adjusting nut lock (16) and lock bolt (18).
6
.
Measure the ring gear to pinion backlash. Refer to
" Backlash Adjustment" in this section.
Tighten
The lock bolt to 30 N-m (22 ft. lbs.) after setting the
backlash.
1
9 /2-INCH RING GEAR 4B3-9
BACKLASH ADJUSTMENT
1. Install a dial indicator to the case using a magnetic
base.
2. Place the indicator stem at the heel end of a tooth.
• Set the dial indicator so that the stem is in line
with the gear rotation and perpendicular to the
tooth angle.
3. Check and record the backlash at three or four
points around the ring gear (figure 22).
• The pinion must be held stationary when
checking backlash.
• The backlash should be the same at each
point within 0.05 mm (0.002-inch). If the
backlash varies
(0.002-inch), check for burrs, a distorted case
flange, uneven bolting conditions, or foreign
matter between the case and the ring gear.
4. Backlash at the minimum lash point measured
should be between 0.125-0.200 mm ± 0.050 mm
(0.005-0.008-inch ± 0.002-inch).
5. If the reading is too high, increase the shim pack
between the differential flange side of the case and
the axle housing (opposite the adjusting nut side).
6. If the reading is too low, decrease the shim pack
between the differential flange side of the case and
the axle housing (opposite the adjusting nut side).
7. Adjust the side bearing preload. Refer to " Side
Bearing Preload Adjustment" earlier in this section.
FINAL ASSEMBLY
Install or Connect (Figure 1)
1. Drive axles. Refer to the proper service manual.
2. RTV to the axle housing cover.
3. Cover (25) and bolts (24) to the axle housing.
Tighten
• The cover bolts (24) to 27 N-m (20 ft. lbs.).
4. Axle housing to the vehicle. Refer to the proper
service manual.
5. Lubricant to the rear axle.
more than 0.05 mm