GMC 1990 Light Truck Repair Manual page 161

SUBJECT
Description.................................................................................................................................................................... 4B3- 1
Checking the Axle Before Disassembly................................................................................................................ 4B3- 1
Disassembly of the Rear Axle................................................................................................................................4B3- 1
Cleaning.................................................................................................................................................................... 4B3- 4
Inspection.................................................................................................................................................................. 4B3- 4
Assembly of the Rear A x le ..................................................................................................................................... 4B3- 5
Gear Tooth Pattern C h e c k ..................................................................................................................................... 4B3-10
Adjustments Affecting Tooth Contact.................................................................................................................. 4B3-10
Specifications.............................................................................................................................................................. 4B3-12
Special Tools................................................................................................................................................................ 4B3-13
The corporate 91 /2-inch ring gear rear axle uses a con­
ventional ring and pinion gear set to transmit the driving
force of the engine to the rear wheels. This gear set trans­
fers this driving force at a 90 degree angle from the pro­
peller shaft to the drive shafts.
This axle is semi-floating. The axle shafts are supported
at the wheel end of the shaft by a roller bearing that is
pressed into the housing. The shafts are retained into the
housing by retaining clips within the differential. The pin­
ion gear is supported by two tapered roller bearings. The
pinion depth is set by a shim pack located between the
gear end of the pinion and the roller bearing that is
pressed onto the pinion. The pinion bearing preload is set
by crushing a collapsable spacer between the bearings in
the axle housing.
The ring gear is bolted onto the differential case with
left-hand thread bolts.
The differential case is supported in the case by two
tapered roller bearings. The differential and ring gear are
located in relationship to the pinion by using selective
shims between the bearing and the axle housing. To move
the ring gear, shims are deleted from one side and an
equal amount are added to the other side. The differential
bearing preload is set by a threaded differential bearing
adjusting nut located between the axle housing and the
differential bearing cap. Two bearing caps are used to
hold the differential into the rear axle housing.
The differential is used to allow the wheels to turn at
different rates of speed while the rear axle continues to
transmit the driving force. This prevents tire scuffing when
going around corners and prevents premature wear on
internal axle parts.
The rear axle is sealed with a pinion seal, a seal at
each axle shaft end, and by RTV sealant between the rear
cover and the axle housing.
All corporate rear axles are identified by the part num­
ber on the right axle tube near the carrier. The carrier
cover does not have a drain plug.
SECTION 4B3
9 1 /2-INCH
CONTENTS
DESCRIPTION
91 2
/ -INCH RING GEAR 4B3-1
r in g g e a r
CHECKING THE AXLE
BEFORE DISASSEMBLY
Inspect
• Remove the axle cover from the rear axle and drain
the axle lubricant into a suitable container.
1. The ring gear backlash. Refer to " Backlash
Adjustment" in this section. This information can be
used to determine the cause of the axle problem. It
will also help when setting up the shim packs for
locating and preloading the differential case.
2. The case for metal chips and shavings. Determine
where these chips and shavings come from, such as
a broken gear or bearing cage.
• Determine the cause-of the axle problem before
disassembly if possible.
DISASSEMBLY OF THE
REAR AXLE
+ + Remove or Disconnect (Figure 1)
Tools Required:
J 8107-3 Differential Side Bearing Remover
Plug
J 22888 Differential Side Bearing Remover
J 8614-01 Pinion Flange Remover
J 22910-01
Remover
• Place the rear axle in a suitable support.
1. The differential cover bolts (24) and the differential
cover (25).
• Drain the gear lub rica nt into a proper
container.
2. Axle shafts (3). Refer to the proper service manual.
3. Outer wheel bearings (5) and seals (14). Refer to the
proper service manual.
PAGE
Rear Pinion B earing Cone