GMC 4000 Series Service Manual page 496

PROBLEM VIBRATION OR SHIMMY
CAUSE 1. Tires, wheels, or brake drums out of balance.
2. Bent wheel or out of round tire.
3. Loose steering linkage components.
4. Wheel loose on hub.
5. Drive line universal joints rough, or defective. This condition may be confused with
steering vibration.
6. Engine m isses or is out of balance, this may also be confused with steering shimmy.
7. Defective shock absorbers.
REPAIR 1. Balance tires and wheels, preferably with on-vehicle type balancer, as this method
balances entire wheel and drum assembly.
2. Replace wheel, and remount tire, or replace.
3. Adjust, tighten, and repair linkage as necessary.
4. Inspect wheel bolt holes for damage, and tighten to proper torque if OK.
5. Repair drive line as described in "PROPELLER SHAFTS" (SEC. 4D) of this manual.
6. Correct m iss in engine, or repair out of balance condition, clutch, pressure plate,
or harmonic balancer etc.
7. Replace shock absorbers.
PROBLEM EXCESSIVE ROAD SHOCK
1. Tire air pressure too high.
CAUSE
2. Wheel bearings adjusted too loose.
3. Camber adjustment incorrect - (negative camber contributes to road shock).
4. Weak or broken front spring.
5. Defective shock absorbers.
6. Loose suspension components.
REPAIR 1. Deflate to correct pressure.
2. Adjust bearings as described in "FRONT HUBS AND BEARINGS" (SEC. 3D).
3. Adjust camber to correct specification as described in "FRONT END ALIGNMENT"
(SEC. 3A) of this manual.
4. Repair or replace spring.
5. Replace shock, or shock absorbers.
6. Inspect, adjust or repair, and replace parts as necessary.
PROBLEM - SNAPPING OR CHUCKING IN STEERING COLUMN OR WHEEL
.
Steering shaft stop clamp loose, this permits excessive up and down movement of
CAUSE 1
steering shaft and wheel in column.
2. Loose steering gear at frame.
3. Worn steering shaft universal joints.
4. Worn steering linkage components. The effect of these components will telescope
through steering system and be felt in steering wheel.
5. Steering gear incorrectly adjusted.
.
Adjust steering shaft stop clamp as described previously in this section.
REPAIR 1
2. Tighten mounting bolts to proper torque listed in "Specifications" at end of this section.
3. Replace and repair joints as necessary.
4. Adjust, tighten and repair components as described previously in this section.
5. Adjust steering gear as previously described in this section.
G M C S E R V I C E M A N U A L
Sec. 9A
Page 485
MECHANICAL STEERING