GMC 4000 Series Service Manual page 116

This group is divided into four sub-sections as shown in index below:
Section
3A
3B
3C
3D
Proper alignment of front wheels must be
maintained to insure efficient steering and sa tis-
factory tire life. The most important factors of
front end alignment are wheel toe-in, wheel cam -
ber, and axle caster. Front end alignment should
be checked at regular intervals, and particularly
after front axle has been subjected to heavy im ­
pacts such as a collision or a hard curb bump.
Before checking alignment, wheel bearings must
be properly adjusted since loose wheel bearings
!r / . , A
will affect instrument readings when checking
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wheel toe-m , wheel camber, and axle caster.
When checking alignment, instructions out-
lined in this section should be followed carefully,
as well as instructions covering related units such
as brakes, springs, steering gear, hubs and bear-
ings, and wheels and tires, which are given in
° , A 1 .
other sections of this manual. Front End Alignment
A
Chart (fig. 1) indicates points at which alignment
dimensions are taken.
The caster, camber, and toe-in dimensions
are for vehicle at design load (with frame level).
If frame is not level on alignment equipment, the
POSSIBLE CAUSE
CONDITION
Noisy Front End 1. Loose tie rod ends.
2. Lack of proper lubrication.
3. Broken spring leaf.
4. Loose U-bolts or spring clips.
Wheel Bounce 1. Unbalanced wheels or tires.
2. Unequal tire pressure.
3. Weak or broken front spring.
4. E xcessive wheel or tire runout.
Excessive Tire Wear 1. Incorrect wheel alignment.
2. Failure to rotate tires.
3. Improper tire inflation.
4. Overloaded or improperly loaded.
G M C S E R V I C E M A N U A L
SECTION 3
Front End Alignment
Front Axle ....................................................................
Front Springs and Shock A b s o r b e r s ......................
Front Hubs and Bearings
SECTION 3A
■
° &
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x
SERVICE DIAGNOSIS CHART
..................................................
...........................................
frame angle must be considered. This is especially
important when making caster check for the frame
angle must be added to the caster angle to obtain a
true setting. All alignment checking should be done
with precision equipment and instruments. Refer
to "Alignment Specifications" at end of this section,
DEFINITION OF TERMS
, . . ,
Distance front wheels are closer together at
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front than at rear of axle (see E and F,"fig. 1).
WHEEL CAMBER
Amount wheels are inclined from vertical
plane (see "C," fig. 1).
FRONT AXLE CASTER
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Inclination of king pin from the vertical in the
e , .. ,,,
fore and aft direction of the vehicle (see "G," fig. 1).
KING PIN INCLINATION
The slant of the king pin toward the center of
the vehicle at the top and outward at the bottom
(see "D," fig. 1).
CORRECTION
1. Replace ends.
2. Refer to LUBRICATION (SEC. 0).
3. Replace spring leaf.
4. Tighten
1. Refer to "Balancing" (SEC. 10).
2. See "Load and Inflation Table" (SEC. 10).
3. Replace.
4. Refer to WHEELS AND TIRES (SEC. 10).
1. Align wheels (SEC. 3A).
2. Refer to WHEELS AND TIRES (SEC. 10).
3. Refer to "Load and Inflation Table"(SEC.10)
4. Avoid overloading vehicle.
Sec. 3A
Page 109
Page No.
109
113
117
122
WHEEL TOE IN
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