GMC 4000 Series Service Manual page 121

Sec. 3B
Page 114
FRONT AXLE
BRAKES" (SEC. 5A) of this manual.
3. Check stop screw s and adjust as previously
described. Check front end alignment factors and
adjust as necessary.
FRONT AXLE OVERHAUL
Steering knuckles, king pins, and bushings or
thrust washers and thrust bearings can be replaced
without removing front axle from vehicle. Minor
axle straightening can also be accomplished with­
out removing assem bly from vehicle. Preliminary
inspection can be made while axle is still mounted.
These inspections should aid in determining the
amount of repair necessary. Check front end align­
ment as directed previously under "FRONT END
ALIGNMENT" (SEC. 3A). Inability to correctly
align wheels indicates that axle center or steering
knuckle is distorted, tie rod bent, or knuckle bush­
ings are worn beyond lim its.
STEERING KNUCKLE
DESCRIPTION
The king pin is held in place with a tapered
draw key, installed as shown in figure 2. The draw
key is retained in place by a lock washer and nut.
1 Steering Knuckle
2 Cap Screw
3 Upper King Pin
Bearing Cap
4 King Pin Bearing Cap
Gasket
5 Lubrication Fitting
6 Shim
7 Draw Key
8 Stop Screw Lock Nut
9 Stop Screw
10 Thrust Bearing
Figure 2— Typical Steering Knuckle Construction
G M C S E R V I C E M A N U A L
14 Lubrication Fitting
15 Lower King Pin
Bearing Cap
16 Spacer - Steering
Knuckle Bushing
(Some Models)
17 Cap Screw
18 King Pin Bearing Cap
Gasket
19 Lower Bushing
O-ring Seal
20
21 Upper Bushing
22 King Pin
T
-3 079
Steering knuckles are equipped with bushings of
polycarbonate construction and they can be washed
in conventional solvents without damage.
Upper and lower ends of knuckles are sealed
with king pin bearing caps and gaskets and an O-
ring seal at the bottom of upper bushings, to p re­
vent lubricant leakage and to exclude dirt and
moisture. Some models are equipped with steering
knuckle bushing spacer (fig. 2). The vertical thrust
loads are carried by thrust bearing or thrust wash­
er installed between lower face of axle center and
steering knuckle lower yoke.
REMOVAL
1. Jack up axle and remove hubs and bearings
as directed in "FRONT HUBS AND BEARINGS"
(SEC. 3D). Remove brake backing plate from steer­
ing knuckle. Remove tie-rod as directed in STEER­
ING SYSTEM (SEC. 9) of this manual.
2. Remove steering arm from steering knuckle.
3. Remove king pin draw key nut and washer.
Thread nut on draw key far enough to protect
threads. Strike nut with hammer to loosen draw
key. Remove nut, then drive pin out with brass
drift and hammer.
4. Remove cap screws attaching upper and
lower king pin bearing caps and gaskets to steer­
ing knuckle, then remove caps and gaskets.
5. Using brass drift and hammer drive king
pin out of axle.
NOTE: On some models, bushing spacer will
be removed at same time as king pin.
6. Remove steering knuckle thrust bearing or
thrust washers, shims, and O-ring.
7. Refer to "Inspection and Repair" later in
this section for inspection and repair procedure.
INSPECTION A N D REPAIR
Wash all parts in cleaning solution. Cap gas­
kets should be discarded and replaced with new
parts. Soak thrust washers and bearings in cleaner
to dissolve lubricant; then brush with soft brush
to remove grit if necessary.
CAUTION: Avoid turning bearings in
races when bearing assemblies are dirty,
since small particles of grit will damage
bearings. "Specifications" at end of this
section itemize the various fits and toler­
ances which apply to all front axles cov­
ered by this manual. It is recommended
that all parts which do not meet these
specifications be replaced.
King pin repair kits are available. The kits
include parts which normally require replacement
at overhaul.