Test Description
The numbers below refer to the step numbers in the diagnostic table.
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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.)
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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.)
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First-order driveline vibrations can be caused by excessive runout of a propeller shaft.
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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.
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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 | |||||
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? | ||||||
6 | Inspect the following components for wear or damage:
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 | -- | ||||
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 | |||||
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 | ||||||
10 | Was the vibration most evident under the transmission mount? | Go to Step 11 | Go to Step 13 | ||||
Measure the runout at the rear of the front axle propeller shaft, if equipped and 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 |
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 |
Was the vibration reduced or eliminated? | Go to Step 26 | Go to Step 17 | ||||
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 . 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 Front Differential Drive Pinion Flange/Yoke, Seal, and Dust Deflector Replacement 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 | -- | ||||
Re-index the propeller shaft. Perform the following steps:
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 | |||||
19 | Inspect the following components for wear or damage:
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 |
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 shafts for proper phasing. Refer to Propeller Shaft Phasing Inspection . Does the propeller shaft phasing require correction? | Go to Step 25 | |||||
25 | Correct the propeller shaft phasing. Refer to Propeller Shaft Phasing Correction . Did you complete the repair? | Go to Step 26 | -- | ||||
26 |
Is the vibration still present? | Go to Step 3 | System OK |
