GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2002 🢒 Express 🢒 General Information 🢒 Vibration Diagnosis and Correction 🢒 Vibration Analysis - Driveline

Test Description

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

  1. First-order driveline related vibrations are usually caused by components that exhibit excessive runout or imbalance. Reproducing a vibration concern in the service stall can aid in pin-pointing the component which may be at fault. (A vibration concern may appear to be either less severe or more severe when duplicated in a service stall, than when duplicated on the road.)

    2.

  2. First-order driveline related vibrations that could not be duplicated during the non-torque sensitive service stall test, could be caused by internal axle components. This test is designed to duplicate first-order driveline related vibrations that are sensitive to torque/load. (A vibration concern may appear to be either less severe or more severe when duplicated in a service stall, than when duplicated on the road.)

    3.

  3. First-order driveline vibrations can be caused by excessive runout of a propeller shaft.

    4.

  4. First-order driveline vibrations can be caused by excessive runout of the pinion flange. If a propeller shaft exhibits excessive runout at a pinion flange end only, the runout may actually be caused by the pinion flange.

    5.

  5. Re-indexing a propeller shaft to a pinion flange can reduce the amount of total combined runout which the components produce, which may in-turn reduce a vibration.

Step

Action

Yes

No

1

Has the Vibration Analysis - Road Testing table been completed?

Go to Step 2

Go to Vibration Analysis - Road Testing

2

Did you record frequency data from the J 38792-A during the Vibration Analysis - Road Testing procedure?

Go to Step 3

Go to Step 5

3

Based on the Vibration Analysis - Road Testing table, is the concern first order driveline related?

Go to Step 6

Go to Step 4

4

Based on the Vibration Analysis - Road Testing table, is the concern second order driveline related?

Go to Step 19

Go to Step 5

5

Based on the Vibration Analysis - Road Testing table, is the concern a noise that is not felt?

Go to Vibration Diagnostic Aids

Go to Vibration Analysis - Road Testing

6

Inspect the following components for wear or damage:

    • Inspect the propeller shafts for dents, damage, missing weights, and undercoating.
    • Inspect the U-joints for damage and missing components.
    • Inspect the propeller shaft support bearing assembly (if applicable) for damaged rubber components, worn bearings, or a cracked bracket.

Are any of the components listed worn or damaged?

Go to Step 7

Go to Step 8

7

Replace the damaged or missing components. Refer to one of the following procedures in Propeller Shaft:

Did you complete the replacement?

Go to Step 26

--

8

Attempt to duplicate the vibration in the stall. Refer to Vibration in Service-Stall Test (Non-Torque Sensitive) .

Were you able to duplicate the vibration?

Go to Step 10

Go to Step 9

9

Perform the Vibration in Service-Stall Test (Torque Sensitive) .

Were you able to duplicate the vibration?

Go to Diagnostic Starting Point - Rear Drive Axle in Rear Drive Axle

Go to Vibration Diagnostic Aids

10

Was the vibration most evident under the transmission mount?

Go to Step 11

Go to Step 13

11

Measure the runout at the front of the forward-most rear axle propeller shaft. Refer to Propeller Shaft Runout Measurement .

Does the runout measurement require that the propeller shaft(s) be replaced?

Go to Step 13

Go to Step 12

12
  1. Replace the transmission mount. Refer to the appropriate procedure, following:
    2. •  Transmission Mount Replacement In Automatic Transmission - 4L60-E
    •  Transmission Mount Replacement In Automatic Transmission - 4L80-E
  2. Perform the Vibration in Service-Stall Test (Non-Torque Sensitive) .

Is the vibration still present?

Go to Step 13

Go to Step 26

13

Measure the runout of the complete propeller shaft(s). Refer to Propeller Shaft Runout Measurement .

Does the runout measurement require that the propeller shaft(s) be replaced?

Go to Step 14

Go to Step 15

14
  1. Replace the propeller shaft. Refer to appropriate procedure in Propeller Shaft:
  2. Perform the Vibration in Service-Stall Test (Non-Torque Sensitive) .

Was the vibration reduced or eliminated?

Go to Step 26

Go to Step 17

15

Determine the runout of the rear axle pinion flange. Refer to Pinion Flange Runout Measurement .

Does the runout measurement require that the pinion flange be replaced?

Go to Step 16

Go to Step 17

16

Replace the pinion flange. Refer to Drive Pinion Flange/Yoke and/or Oil Seal Replacement in Rear Drive Axle.

Did you complete the replacement?

Go to Step 26

--

17

Re-index the propeller shaft. Perform the following steps:

  1. Raise the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.
  2. Mark the position of the shaft on the pinion flange.
  3. Remove the propeller shaft from the pinion flange.
  4. Rotate the propeller shaft 180 degrees in the pinion flange.
  5. Reinstall the propeller shaft.
  6. Attempt to duplicate the vibration in the stall. Refer to the Vibration in Service-Stall Test (Non-Torque Sensitive) .

Was the vibration reduced or eliminated?

Go to Step 26

Go to Step 18

18

Return the propeller shaft to it's original position and balance the propeller shaft. Refer to Driveline System Balance Adjustment .

Were you able to balance the driveline system?

Go to Step 26

Go to Vibration Diagnostic Aids

19

Inspect the following components for wear or damage:

    • Inspect the propeller shafts for dents, damage, missing weights, and undercoating.
    • Inspect the U-joints for damage and missing components.
    • Inspect the propeller shaft support bearing assembly (if applicable) for damaged rubber components, worn bearings, or a cracked bracket.

Are any of the components listed worn or damaged?

Go to Step 20

Go to Step 21

20

Replace the damaged or missing components. Refer to one of the following procedures in Propeller Shaft:

Did you complete the replacement?

Go to Step 26

--

21
  1. Measure the vehicle trim height.
  2. Adjust the vehicle trim height, if necessary.

Refer to Trim Height Inspection in Suspension General Diagnosis.

Did you find and correct a condition?

Go to Step 26

Go to Step 22

22

Measure the propeller shaft angles. Refer to Driveline Working Angles Measurement .

Do the propeller shaft angles require adjustment?

Go to Step 23

Go to Step 24

23

Adjust the propeller shaft angles. Refer to Driveline Working Angles Adjustment .

Did you complete the repair?

Go to Step 26

--

24

Inspect the propeller shaft(s) for proper phasing. Refer to Propeller Shaft Phasing Inspection .

Does the propeller shaft phasing require correction?

Go to Step 25

Go to Vibration Diagnostic Aids

25

Correct the propeller shaft phasing. Refer to Propeller Shaft Phasing Correction .

Did you complete the repair?

Go to Step 26

--

26
  1. Install or connect any components that were removed or disconnected during diagnosis.
  2. Perform the Vibration Analysis - Road Testing table. Refer to Vibration Analysis - Road Testing .

Is the vibration still present?

Go to Step 3

System OK