Warning: Refer to Road Test Warning in the Preface section.

Did you review the Diagnostic Starting Point - Vibration Diagnosis?

Go to Step 2

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

Go to Step 6

Go to Step 3

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

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

Go to Step 5

Go to Step 4

Note: Do NOT operate the vehicle until the faults are corrected.

Correct the faults with the tyre and wheel assemblies, steering components, and/or the suspension components before proceeding.

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

Go to Step 5

Go to Step 3

5

1. Obtain the drive shaft final drive ratio.
2. If the GE-38792-VS Vibrate Software, IS available, obtain the transmission gear ratios.
3. If the GE-38792-VS Vibrate Software is NOT available, take note of the tyre size on each axle, then calculate the tyre rotational speed for each size tyre used. Refer to Component Rotational Speed Calculation .

Did you obtain the powertrain ratios for use with the GE-38792-VS Vibrate Software, or calculate the component rotational speeds, if GE-38792-VS Vibrate Software is NOT available?

Go to Step 6

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1. Install a scan tool.
2. With the scan tool, bring up the Powertrain Control Module data list and select Engine Speed.

Is the scan tool operating properly?

Go to Step 7

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Using the GE-38792-VS Electronic Vibration Analyzer 2 (EVA 2), is the preferred method for gathering necessary vibration frequency data.

If the GE-38792-VS Electronic Vibration Analyzer 2 (EVA 2) is not available, the necessary vibration frequency data will have to be obtained based on symptoms observed during testing. Review Symptoms - Vibration Diagnosis and Correction to become familiar with the possible frequency ranges.

Is the GE-38792-VS Electronic Vibration Analyzer 2 (EVA 2) available for use?

Go to Step 8

Go to Step 9

Install the GE-38792-VS Electronic Vibration Analyzer 2 (EVA 2).

Is the GE-38792-VS Electronic Vibration Analyzer 2 (EVA 2) operating properly?

Go to Step 9

Go to Electronic Vibration Analyzer (EVA) Description and Operation

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

Go to Vibration Analysis - Engine

Go to Step 10

10

1. Install the GE-38792-VS Electronic Vibration Analyzer 2 (EVA 2) sensor, if available, to the component identified by the customer as most respondent to the vibration. If no component was identified, install the GE-38792-VS Electronic Vibration Analyzer 2 (EVA 2) sensor, if available, to the steering column. You may have to move the sensor to other locations later.
2. Select a smooth, level road and slowly accelerate the vehicle up to motorway speed.
3. Observe the vehicle for disturbances that match the customer description and note the following conditions:

•	The vehicle speed

•	The engine RPM

•	The transmission gear range and the specific gear

•	The vibration frequency reading, if detected by the GE-38792-VS Electronic Vibration Analyzer 2 (EVA 2)

•	The feel and/or sound of the disturbance

4. If the vibration seems to excite a particular component of the vehicle more than the steering column, then move the GE-38792-VS Electronic Vibration Analyzer 2 (EVA 2) sensor, if available, onto that component and repeat steps 2 and 3.

Were you able to duplicate the customer concern?

Go to Step 11

Go to Vibration Diagnostic Aids

11

1. Accelerate the vehicle to a speed higher than the speed at which the disturbance occurs.

Note: If the vehicle is equipped with an automatic transmission, let the vehicle freewheel to a stop before shifting back into gear.

2. Shift the vehicle into NEUTRAL and allow the vehicle to freewheel down through the disturbance range.

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

Go to Step 13

Go to Step 12

12

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

Go to Vibration Analysis - Hub and/or Axle Input

Go to Vibration Analysis - Engine

If the GE-38792-VS Electronic Vibration Analyzer 2 (EVA 2) is not available, refer to Symptoms - Vibration Diagnosis and Correction .

Did the GE-38792-VS Electronic Vibration Analyzer 2 (EVA 2) detect a dominant frequency?

Go to Step 14

Go to Symptoms - Vibration Diagnosis and Correction

1. If the GE-38792-VS Vibrate Software IS available, use the drive axle final drive ratio, the specific transmission gear ratio, and the engine RPM to make a comparison to the dominant frequency reading recorded.
2. If the GE-38792-VS Vibrate Software is NOT available, compare the dominant frequency reading recorded to the component rotational data which you calculated previously.

Does the frequency data clearly fall within the tyre/wheel parameters ONLY?

Go to Vibration Analysis - Tyre and Wheel

Go to Symptoms - Vibration Diagnosis and Correction