GMC 4000 Series Service Manual page 122

THRUST WASHERS OR BEARINGS
Examine thrust washers or bearings for ex­
ce ssiv e wear or damage. If thrust washer dust
caps are damaged, replace. Replace all parts which
show excessive wear.
STEERING KNUCKLE BUSHINGS
Replace steering knuckle bushings if wear is
indicated, or if results given previously under
"Front Wheel Camber" indicate replacement is
necessary.
BUSHING REPLACEMENT
Removal
Bushings are split, and of Polycarbonate con­
struction, and are hand push fit in knuckle. To re­
move, slide bushings out of bore in knuckle yoke.
Installation
Before installing bushings, remove nicks and
burrs in knuckle yokes and polish with medium
grit abrasive paper or cloth. Apply lubricant sp eci­
fied in LUBRICATION (SEC. 0) of this manual, to
all parts. Push bushings into knuckle bores with
split in bushings aligned with lubrication fitting.
KING PIN INSPECTION
Check diameter of king pin. Also check for
minute cracks or other damage. If inspection re­
veals excessive wear, replace king pin.
AXLE CENTER
There are two conditions which, if either
exists, will necessitate replacement of axle center:
1. If king pin holes in axle center ends are
worn to such an extent that a new oversize king
pin fits loosely, axle center must be replaced.
2. If axle center has been twisted or bent
more than 5 degrees from original shape, center
should be replaced. As a general rule, when an
extreme bent condition exists, minute fractures
which may be invisible will occur, and failure un­
der ordinary operating conditions will result. Check
axle center for twist with alignment instruments,
or on a bench as illustrated in "FRONT END
ALIGNMENT" (SEC. 3A) in figure 3. If equipment
is available, use Magna-Flux method to check axle
center for minute fractures.
NOTE: AXLE CENTERS SHOULD ALWAYS
BE STRAIGHTENED COLD. UNDER NO CIRCUM­
STANCES SHOULD HEAT BE APPLIED.
STEERING KNUCKLES
After steering knuckles have been thoroughly
cleaned, examine knuckles for distortion, cracks,
G M C S E R V I C E M A N U A L
or fractures. If Magna-Flux equipment is avail­
able, use this method to inspect knuckles for frac­
tures which otherwise would not be visible. Replace
steering knuckles if inspection reveals defects
which would affect serviceability.
INSTALLATION
then coat king pin with light coat of engine oil.
thrust bearing into place.
place steel washer between bronze washers, with
lubricating grooves facing steel washer. Always
place larger dust shield over top of washers.
bushing.
yoke, axle end, thrust bearing or thrust washer,
then partially install king pin through top.
under steering knuckle; then raise until all clea r­
ance between knuckle lower yoke, thrust bearing or
thrust washer and axle center is taken up. Check
clearance between top of axle center and knuckle
upper yoke. If clearance exceeds 0.005", place a
shim between axle center and knuckle upper yoke.
pin registering with draw key hole in axle center.
Install king pin from top, inserting through ste er­
ing knuckle yoke, shim, thrust bearing or thrust
washer and axle center end. P ress pin down until
milled slot in pin lines up with draw key hole.
ing with king pin, then install lock washer and nut.
Tighten nut firm ly. It nut bottoms on knuckle be­
fore king pin is secure, replace draw key or use
a draw key with more taper.
spacer, install spacer at lower end of king pin.
lower king pin bearing caps with cap screw s. Tight­
en cap screw s to torque listed in "Specifications."
brication fittings as directed in LUBRICATION
(SEC. 0). Try action of steering knuckle for bind­
ing condition.
tie-rod as directed in STEERING SYSTEM (SEC.
9) of this manual. Install brake backing plate a s­
sem bly. Install hubs and bearings as directed in
"FRONT HUBS AND BEARINGS" (SEC. 3D) of this
manual.
adjustment as previously directed.
1. Before assem bly, thoroughly clean all parts;
2. Position steering knuckle on axle, then slide
NOTE: On models shown in inset of figure 2
3. Install a new O-ring seal at bottom of upper
4. Align king pin holes in steering knuckle
5. With axle center held firm ly, place a jack
6. Install king pin, with milled slot in side of
7. Insert draw key into axle center, reg ister­
8. On models using steering knuckle bushing
9. Install new gaskets, then install upper and
10. Lubricate king pins thoroughly through lu­
11. Install steering arm s to knuckles. Install
12. Check front end alignment and stop screw
Sec. 3B
Page 115
FRONT AXLE