GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2006 🢒 TopKick C-Series (Conventional) C6/C7/C8 🢒 General Information 🢒 Vibration Diagnosis and Correction 🢒 Vibration Analysis - Road Testing

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. Accelerate to a speed high enough above the speed of the disturbance to allow for the time needed to shift into NEUTRAL and for the engine to decrease in RPM to idle speed, before coasting down through the disturbance range.

    2.

  2. This test will either eliminate or confirm the engine as a contributing cause of the customer concern.

Step

Action

Yes

No

Caution: Road test a vehicle under safe conditions and while obeying all traffic laws. Do not attempt any maneuvers that could jeopardize vehicle control. Failure to adhere to these precautions could lead to serious personal injury and vehicle damage.

 

1

Did you review the Diagnostic Starting Point - Vibration Diagnosis?

Go to Step 2

Go to Diagnostic Starting Point - Vibration Diagnosis and Correction

2

Visually inspect the tire and wheel assemblies, steering components and suspension components for any possible faults.

Are the tire and wheel assemblies, steering components and suspension components in good working condition?

Go to Step 4

Go to Step 3

3

Important:: Do NOT operate the vehicle until the faults are corrected. Correct the faults with the tire and wheel assemblies, steering components, and/or suspension components before proceeding.

Did you correct the faults with the tire and wheel assemblies, steering components, and/or suspension components?

Go to Step 4

Go to Step 2

4

Did the customer concern indicate that the vibration occurs ONLY while the vehicle is standing still?

Go to Vibration Analysis - Engine

Go to Step 5

5
  1. Select a smooth, level road and slowly accelerate the vehicle up to highway speed.
  2. Observe the vehicle for disturbances that match the customer's description and note the following conditions:
    3. • The vehicle speed
    • The engine RPM
    • The transmission gear range and the specific gear
    • The feel and/or sound of the disturbance

Were you able to duplicate the customer's concern?

Go to Step 6

Go to Vibration Diagnostic Aids

6

  1. Accelerate the vehicle to a speed higher than the speed at which the disturbance occurs.
  2. Shift the vehicle into NEUTRAL and allow the vehicle to coast down through the disturbance range.

Does the disturbance still occur while coasting-down in NEUTRAL?

Go to Vibration Analysis - Tire and Wheel

Go to Step 7

7

  1. Select a smooth, level road and slowly accelerate the vehicle up to the speed at which the disturbance occurs.
  2. Decelerate and safely downshift by one gear range.
  3. Operate the vehicle at the same VEHICLE SPEED at which the disturbance occurs.

Does the disturbance still occur while going the same vehicle speed in a lower gear range?

Go to Vibration Analysis - Driveline

Go to Vibration Analysis - Engine