GMC PD-4103 Maintenance Manual page 9

Sec. 1
Page 10
GM COACH MAINTENANCE MANUAL
FRONT AXLE REPAIR
1 King Pin Nut
2 King Pin Cover
3 King Pin Bushing
4 Spacing Washer
5 Axle Center End
6 King Pin
7 Expansion Plug
8 Steering Knuckle
Bushing
9 Thrust Bearing
Assembly
10 Steering Knuckle
TP-6335
Figure 2-Steering Knuckle Cross Section
Stop screws installed at each end of center limit
turning angle of front wheels.
FRONT AXLE GENERAL MAINTENANCE
INSPECTION
Following inspection operations should be per-
formed at intervals determined by severity of
service.
L Inspect spring U-bolts for tightness. Tight-
en as directed in SPRING SUSPENSION (SEC. 15).
2. Inspect and tighten tie rod arm and steer-
ing arm nuts. Torque specifications are shown
in "Specifications" at end of this section.
3. Inspect steering arm and tie rod arm nuts
for looseness. Tighten if necessary. Also inspect
tie rod end stud nuts for looseness and check tie
rod ends for wear.
4. When steering difficulty or abnormal tire
wear indicate necessity, check front end align-
ment as previously instructed under "Front End
Alignment."
5. Check stop screws and adjust when neces-
sary. Stop screw adjustment procedure is des-
cribed later.
6. Lubricate front axle parts as instructed
in LUBRICATION (SEC. 13).
7. When lubricating front axle parts, observe
condition of seals at steering knuckle, tie rod ends,
and drag link. If seals are found to be damaged
or missing, new seals should be installed imme-
diately.
8. Periodical inspection should be made at
steering knuckles to determine if excessive up-
and-down movement of knuckles on king pins
exists. Since excessive pounding will damage
thrust bearing (9, fig. 2) the up-and-down move-
ment of steering knuckles must be kept within
prescribed limits. Shims for use in reducing
clearance are available. Refer to "ADJUSTMENTS"
later in section for method of checking clearance
and making shim installation.
ADJUSTMENTS
A number of difficulties found during front end
alignment check can be corrected by making ad-
justments at front axle assembly. Among these
adjustments are; wheel bearing adjustment, tie
rod and drag link adjustment, stop screw adjust-
ment and brake adjustment. All the above men-
tioned adjustment procedures except tie rod and
stop screw adjustment are covered in other sec-
tions of manual.
TIE ROD ADJUSTMENT
Tie rod adjustment is necessary whenever
front wheel toe-in is found to be incorrect. Ad-
just tie rod as follows:
1.
Set front wheels in straight-ahead position.
2. Loosen clamp bolts at both ends of tie rod.
3. Use pipe wrench to turn tie rod tube as
required to correct toe in measurement. Refer
to "FRONT END ALIGNMENT" previously in this
section for method of measuring toe-in.
4. When adjustment is completed, make sure
tie rod ends are in same plane, then tighten
clamp bolts.
STOP SCREW ADJUSTMENT
Stop screws installed in front axle center limit
front wheel turning angle to right and left. Stop
screws must be set properly to give equal turn-
ing radius to the right and to left, as well as to
limit turning angle and thereby prevent interfer-
ence between front tires and other parts of coach.
Before setting stop screws, refer to STEER-
ING GEAR (SEC. 16) and be sure pitman arm is
properly installed on steering gear and be sure
steering gear drag link is properly adjusted for
length and not distorted or bent.
Adjust stop screws as follows:
1. Raise front axle until front wheels are off
floor.
2. Turn front wheels to extreme left. In this
position there should be
1 /2
inch clearance be-
tween tire and drag link. If necessary, turn stop
screw in or out to provide 1 /2 inch clearance
mentioned above. Secure stop screw setting with
lock nut.
3. With wheels turned to extreme left posi-
tion measure and record distance from left front
tire to outer edge of front spring at nearest point.