GMC 1989 Light Duty Truck, Repair Manual, Page: 290 / 998

4C4-2 K TRUCK FRONT AXLE
DESCRIPTION
The front axle on K model vehicles has a center discon­
nect feature which, under most conditions, allows shifting
into and out of four wheel drive when the vehicle is in
motion. It is operated by a therm al actuator solenoid.
The axle uses a conventional ring and pinion gear set to
transm it the driving force of the engine to the wheels. The
pinion gear is supported by two tapered roller bearings. The
pinion depth is set by a shim located between the gear end
of the pinion and the roller bearing that is presed onto the
pinion. The pinion bearing preload is set by crushing a
collapsible spacer between the pinion bearings in the axle
housing.
The ring gear is bolted onto the differential case with left-
hand thread bolts.
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 prem ature wear on
internal axle parts.
The differential case is supported in the axle housing by
two tapered roller bearings. The differential and ring are
located in relationship to the pinion by using threaded
adjusters.
The axle id e n tifica tio n num be r is located on a tag
attached to the right axle tube.
The axle is produced with 8 1/4 inch and 9 1/4 inch ring
gears. The
8
V
4
inch ring gear is used on K15-25 models; the
91/4
inch ring gear is used on K35 models.
The drive axles are com pletely flexible assem blies con­
sisting of inner and outer constant velocity (CV) joints pro­
tected by therm oplastic boots and connected by an axle
shaft.
DISASSEMBLY OF AXLE
INSPECTION
Perform the following checks before disassem bling the
axle.
1 . Remove the drain plug from the axle and drain the
axle lubricant into a suitable container.
2. Check the ring gear backlash. Refer to “ Adjusting
Backlash.” This information can be used to deter­
mine the cause of the axle problem. It will also help
when setting up the shim packs for locating and pre-
loading the differential case.
3. Inspect the case for metal chips. Determine where
the metal chips come from, such as a broken gear or
bearing cage.
4. Determine the cause of the axle problem before dis­
assembly if possible.
DISASSEMBLY
«--► Remove or Disconnect (Figures 1 through 19)
Tools Required:
J 29369-1 Bearing Remover (K15-25 Models)
J 29369-2 Bearing Remover (K35 Models)
J 29307 Slide Hammer
J 34011 Pilot Bearing Remover
J 36599 Adjusting Sleeve W rench
J 36615 Adjuster W rench (K35 Models)
J 8614-01 Pinion Flange Remover
J 36598 Holding Fixture and Pinion Service
Tool
J 8612-B Pinion Bearing R em over (K15-25
Models)
J 36606 Pinion Bearing Remover (K35 Models)
J 22888-D Side Bearing Puller
J 8107-2 Side Bearing Puller Pilot (K15-25 Mod­
els)
J 36597 Side Bearing Puller Pilot (K35 Models)
J 36616 Bushing Replacer
1. Solenoid (10)
2. Indicator Switch (13)
3. Bolts (6).
4. Tube (5) with shaft (1).
5. Sleeve (22).
6. Shift shaft (18), dam per spring (17), shift fork (16), and
clip (15) assembly.
7. Spring (14).
8. Shim (20).
9. Carrier connector (9) with retainer ring (8) (K15-25
models).
• Clam p the tube (5) in a vise. Clam p only on the
m ounting flange.
• Strike the inside of the shaft (1) flange with a
brass ham mer to dislodge the carrier connec­
tor.
10. Snap ring (12) and washer (11) and thrust washer (7)
(K35 models) (figure 5).
11. Shaft (1) with deflector (2).
12. Seal (3) and bearing (4). Use J 29361-1 (K15-25 mod­
els) or J 29369-2 (K35 models) w ith J 29307 (figure 6).
13. Output shaft (23).
14. Differential pilot bearing (21). Use J 34011 (figure 7).
15. Shaft (59) with deflector (2). Pry on the shaft flange on
one side while tapping with a soft faced ham mer on
the other side (figure 8).
16. Seal (3). Pry out with a screwdriver.
17. Bearings (30). Use the tools listed in step 10.
18. Bolts (28).
19. Right side carrier half (29). Tap on the cast lugs pro­
vided.
20. Differential assembly.
• Pry up on the locks (51) (right side only on K35).
21. Bolt (64) and lock (63) (K35 models).