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Test Description

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

  1. 8:  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. 9:  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 duplicated 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. 11:  First-order driveline vibrations can be caused by excessive runout of a propeller shaft.
  4. 15:  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. 17:  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.
Vibration Analysis - Driveline

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?. See Special Tools and Equipment . 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.

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 rear of the front axle propeller shaft, if equipped and measure the runout at the front of the rear axle propeller shaft. Refer to Propeller Shaft Runout Measurement (One-Piece)  .
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 Transmission Mount Replacement (4.2L) or Transmission Mount Replacement (5.3L) in Automatic Transmission - 4L60-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 (One-Piece)  .
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 front axle pinion flange, if equipped, and determine the runout of the rear axle pinion flange. Refer to the Pinion Flange Runout Measurement (System Balanced Flange)  .
Does the runout measurement require that the (front and/or rear) pinion flange be replaced?		 Go to Step 16  Go to Step 17 
16 Replace the pinion flange. Refer to Differential Drive Pinion Flange/Yoke, Seal, and Dust Deflector Replacement - Front in Front Drive Axle and/or 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 (Using EVA)  .
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.

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 Procedure 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 shafts 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
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