GMC 4000 Series Service Manual page 120

Axle steering knuckles are constructed as
shown in figure 2. Wheel bearings, springs, steer­
ing, and brake parts which are mounted on front
axle are described in their respective section in
this manual. Front axle specifications are given at
end of this section.
MAINTENANCE O N VEHICLE
Following maintenance operations should be
performed at intervals determined by severity of
service:
1. Inspect spring U-bolts for tightness. If
loose, tighten as directed in "FRONT SPRINGS"
(SEC. 3C).
2. Inspect and tighten all ball stud nuts.
3. Examine steering knuckle bearing caps for
tightness and evidence of lubricant leakage. Tighten
or replace parts as required.
4. Inspect and tighten king pin draw key nuts.
Loose draw keys will permit king pin to turn in
axle center, thus enlarging king pin hole. If hole
becom es too greatly enlarged, replacement of axle
center may be necessary. If draw key holes become
enlarged beyond use of new key, replace axle cen­
ter. IT IS NOT SAFE TO REAM AND BUSH DRAW
KEY HOLES.
5. Check vertical movement of knuckle on king
pin as directed under "Axle Overhaul" later.
STOP SCREWS
Stop screws shown in figure 1 for F-040,
F-050 and F-055 axles are installed on steering
arm.3 and stop against axle center. Stop screw s for
F-070 axles are installed in the steering knuckles
and stop against the axle center. If stop screws are
set in too far, road shock may impose excessive
load on steering gear, and worm shaft nut may
bottom on housing end cover before stop screws
contact axle center.
Place each wheel on wheel alignment instru­
ment and adjust stop screw s as shown in figure 1.
When oversize tires are installed, the turning
clearance should be checked. A minimum clearance
of 5/8" should be maintained between chassis and
tires. If specified clearance does not exist, read­
just knuckle stop screws to obtain the proper
clearance.
FRONT AXLE REPLACEMENT
All component parts of the front axle assem ­
bly except axle center can be replaced without re­
G M C S E R V I C E M A N U A L
SECTION 3B
fy n a n t A x lz
moving assembly from vehicle if necessary. Minor
straightening with suitable equipment can be ac­
complished with assembly in vehicle. When the
front axle requires a complete overhaul, the a s ­
sembly can be replaced as described in following
procedures:
REMOVAL
lieve load from front springs.
lines to axle. Disconnect drag link from steering
arm.
jack, remove spring U-bolts. Lower assembly and
remove from under vehicle.
INSTALLATION
tion under vehicle. Raise axle up against springs,
making sure spring center bolts enter alignment
holes in spring seats. Be sure caster axle shim s,
if used, are in place between spring and axle with
thick edge of caster spacer facing proper direction
as indicated in figures 2 and 3 of "FRONT SPRINGS"
(SEC. 3C) of this manual. Attach axle to springs,
tightening the U-bolts as described in "FRONT
SPRINGS" (SEC. 3C) of this manual.
"FRONT HUBS AND BEARINGS" (SEC. 3D). Con­
nect drag link as directed in STEERING SYSTEM
(SEC. 9). Connect brake lines. If hydraulic brakes
are used, bleed as described in "HYDRAULIC
1. Jack up and support vehicle frame to re­
2. Remove wheels and hubs. Disconnect brake
3. While supporting axle center with suitable
1. Place assembly on dolly and roll into posi­
2. Install hubs and bearings as described in
Sec. 3B
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