GMC 1989 Light Duty Truck Repair Manual page 271

T TRUCK FRONT AXLE
S U B J E C T
D escription....................................................................................................................................................................................4 C 3 - 1
Disassembly of A x le ..................................................................................................................................................................4 C 3 - 2
Inspection..................................................................................................................................................................................4 C 3 - 2
D isassem bly............................................................................................................................................................................. 4C 3- 2
Cleaning and Inspectio n ........................................................................................................................................................... 4C 3- 7
C le a n in g .................................................................................................................................................................................... 4C 3- 7
Inspection..................................................................................................................................................................................4C 3- 7
Assembly of A xle.........................................................................................................................................................................4 C 3 - 8
Differential Case A ssem bly..................................................................................................................................................4C 3- 8
Pinion Bearing Cup In s ta lla tio n .........................................................................................................................................4C 3- 8
Pinion Depth A d ju s tm e n t.................................................................................................................................................... 4 C 3 - 9
Pinion In s ta lla tio n ..................................................................................................................................................................4 C 3 - 9
Differential Assembly In s ta lla tio n .........................................................................................................................................4 C 3 - 9
Adjusting B ac klas h .................................................................................................................................................................... 4 C 3 - 9
Gear Tooth Contact Pattern C h e c k ...................................................................................................................................... 4C 3 -1 3
Final A ssem bly.........................................................................................................................................................................4C 3-13
S p e c ific a tio n s ............................................................................................................................................................................. 4C 3 -1 6
Special T o o ls ............................................................................................................................................................................... 4 C 3 -1 7
The axle used on T model vehicles has a center discon­
nect feature which allows shifting into and out of four
wheel drive when the vehicle is in motion under most con­
ditions.
The axle uses a conventional ring gear and pinion gear
set to transmit the driving force of the engine to the
wheels. This gear set transfers this driving force at a 90
degree angle from the propeller shaft to the drive shafts.
The pinion gear is supported by two tapered roller bear­
ing. The pinion depth is set by a shim pack located be­
tween the gear end of the pinion and the roller bearing
that is pressed onto the pinion. The pinion bearing pre­
load is set by crushing a collapsible spacer between the
pinion bearings in the axle housing.
T TRUCK FRONT AXLE 4C3-1
SECTION 4C3
CONTENTS
DESCRIPTION
The ring gear is bolted onto the differential case with
left-hand thread bolts.
The differential case is supported in the axle housing
by two tapered roller bearings. The differnetial and ring
gear are located in relationship to the pinion by using
threaded adjusters.
The differential is used to allow the wheels to turn at
different rates of speed while the front axle continues to
transm it the driving force. This prevents tire scuffing when
going around corners and prevents premature wear on
internal axle parts.
The axle identification num ber is located on a tag at­
tached to the right axle tube.
P A G E