GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2005 🢒 STS 🢒 General Information 🢒 Vibration Diagnosis and Correction 🢒 Vibration Analysis - Driveline

Test Description

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

  1. In most cases, the vibration can be reproduced in the stall, but it is either not as bad or a lot worse than experienced on the road. This is normal. First-order driveline vibrations may be caused the imbalance of a component. The In-Stall test will help determine which component needs to be repaired or replaced.

    2.

  2. If the vehicle has a vibration that is equal to first-order driveline rotation, and it is not present when testing the vehicle in the stall, then it is possible that the vibration is being generated by internal rear axle components. This may also be true if the vibration was correctable in the stall but returned when the vehicle was driven on the road.

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 Electronic Vibration Analyzer (EVA) 2 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 21

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 propeller shafts for dents, damage, missing weights, and/or undercoating.
    • Inspect the U-Joint for excessive wear, looseness, and/or damage.
    • Inspect the propeller shaft support bearing assembly for damaged rubber components, worn bearings, and/or a deformed or cracked bracket.

Did any of the components listed exhibit any of the conditions listed?

Go to Step 7

Go to Step 8

7

Replace the components as necessary. Refer to one of the following procedures in Propeller Shaft:

Did you complete the overhaul or replacement?

Go to Step 28

--

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
  1. With the vehicle still supported on a hoist, have an assistant run the vehicle at the concern speed while you perform the following steps.
    2. 1.1. Position and use light pressure to hold the J 38792-A sensor to the underside of the transmission mount bracket. Record the amplitude of the vibration on the J 38792-A .
    1.2. Position and use light pressure to hold the J 38792-A sensor to the underside of the rear drive axle pinion housing. Record the amplitude of the vibration on the J 38792-A .
  2. Determine which of the 2 locations exhibited the greatest amplitude on the J 38792-A .

Did you complete the operation?

Go to Step 11

--

11

Was the vibration most evident under the transmission mount?

Go to Step 12

Go to Step 14

12
  1. Inspect the front propeller shaft coupler assembly for excessive wear, looseness, and/or damage.
  2. Inspect the transmission mount for excessive wear and/or damage.

Did any of the components listed exhibit any of the conditions listed?

Go to Step 13

Go to Step 15

13
  1. Replace the components as necessary, refer to the following procedures:
    2. •  Front Propeller Shaft Replacement in Propeller Shaft
    •  Rear Propeller Shaft Replacement in Propeller Shaft
    •  Transmission Mount Inspection in Automatic Transmission - 5L40-E/5L50-E
  2. Perform the Vibration in Service-Stall Test (Non-Torque Sensitive) .

Is the vibration still present?

Go to Step 15

Go to Step 28

14

Was the vibration most evident under the propeller shaft support bearing assembly?

Go to Step 15

Go to Step 17

15
  1. Inspect the U-Joint for excessive wear, looseness, and/or damage.
  2. Inspect the propeller shaft support bearing assembly for damaged rubber components, worn bearings, and/or a deformed or cracked bracket.

Did any of the components listed exhibit any of the conditions listed?

Go to Step 16

Go to Step 17

16
  1. Replace the components as necessary. Refer to the following procedures in Propeller Shaft:
  2. Perform the Vibration in Service-Stall Test (Non-Torque Sensitive) .

Is the vibration still present?

Go to Step 17

Go to Step 28

17
  1. Inspect the rear propeller shaft coupler assembly for excessive wear, looseness, and/or damage.
  2. Inspect the rear drive axle damping bushings for excessive wear and/or damage.

Did any of the components listed exhibit any of the conditions listed?

Go to Step 18

Go to Step 19

18
  1. Replace the components as necessary. Refer to the following procedures:
    2. •  Front Propeller Shaft Replacement in Propeller Shaft
    •  Rear Propeller Shaft Replacement in Propeller Shaft
    • Damping Bushing Replacement - Front or Damping Bushing Replacement - Rear in Rear Drive Axle
  2. Perform the Vibration in Service-Stall Test (Non-Torque Sensitive) .

Is the vibration still present?

Go to Step 19

Go to Step 28

19

Visually inspect the rear axle pinion flange for damage.

Does the pinion flange exhibit any damage?

Go to Step 20

Go to Step 25

20
  1. Replace the pinion flange. Refer to Drive Pinion Flange/Yoke and/or Oil Seal Replacement in Rear Drive Axle.
  2. Perform the Vibration in Service-Stall Test (Non-Torque Sensitive) .

Is the vibration still present?

Go to Step 25

Go to Step 28

21
    • Inspect the propeller shafts for dents, damage, missing weights, and/or undercoating.
    • Inspect the U-Joint for excessive wear, looseness, and/or damage.
    • Inspect the propeller shaft support bearing assembly for damaged rubber components, worn bearings, and/or a deformed or cracked bracket.

Did any of the components listed exhibit any of the conditions listed?

Go to Step 22

Go to Step 23

22
  1. Replace the components as necessary. Refer to one of the following procedures in Propeller Shaft:
  2. Perform the Vibration in Service-Stall Test (Non-Torque Sensitive) .

Is the vibration still present?

Go to Step 23

Go to Step 28

23

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

Does the propeller shaft angle require adjustment?

Go to Step 24

Go to Step 27

24
  1. Adjust the propeller shaft angle. Refer to Driveline Working Angles Adjustment .
  2. Perform the Vibration in Service-Stall Test (Non-Torque Sensitive) .

Is the vibration still present?

Go to Step 27

Go to Step 28

25

Balance the propeller shafts. Refer to Driveline System Balance Adjustment .

Were you able to balance the driveline system?

Go to Step 26

Go to Vibration Diagnostic Aids

26

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

Is the vibration still present?

Go to Step 27

Go to Step 28

27

Replace the propeller shaft. Refer to the following procedures in Propeller Shaft:

Did you complete the replacement?

Go to Step 28

--

28
  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