On-Vehicle Service; Idler Arm Inspection - GMC G Service Manual

3B1-2 STEERING LINKAGE

IDLER ARM INSPECTION

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Inspect (Figures 4 and 5)
1. Raise the vehicle. Be sure that the front wheels rotate
freely, the steering mechanism turns freely, and the
wheels are positioned straight ahead.
2. Position a dial indicator against the top of the idler
arm grease cap.
3. Place a spring scale near the relay rod end of the idler
arm.
• Apply a 110 N (25 lb.) force upward and then
downward. (On G-models the force is forward
and rearward.)
4. Measure the total distance the idler arm moves under
the applied force specified.
• Allow no more than ±3.18 mm (1/8 in.) deflec­
tion in each direction, for a total of 6.32 mm (1/4
in.) (figures 4 and 5).
1. Idler Arm
2. Relay Rod
3. Tie Rod Assembly
4. Steering Knuckle
5. Pitman Arm
6. Steering Gear
16. Idler Arm Frame Support
Figure 1 — Steering Linkage —- R-Model, Typical of P20, and P30 Models (except Motorhome)

ON-VEHICLE SERVICE

5. Replace the idler arm if it fails this test. Refer to "Idler
Arm Replacement" in this section.
• For P30 Motorhomes, the idler arm is adjustable.
Refer to "Idler Arm Adjustment — P30 Motorhome" in
this section. If replacement is necessary, refer to
"Idler Arm Replacement" in this section.
] Important
• Jerking the right wheel and tire assembly back and
forth to cause an up and down movement of the idler
arm, is NOT an acceptable testing procedure. There
is no control on the amount of force being applied to
the idler arm.
• Loose idler arms or other suspension or steering sys­
tem defects can create a shimmy condition. Shimmy
problems may also originate at the wheel and tire
assembly from dynamic imbalance, run out or force
variations, or even road surface irregularities. Con­
sider all possible causes of a shimmy complaint.
Refer to WHEELS AND TIRES (SEC. 3E).
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