For 1990-2009 cars

### Test Description

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

1. If clearance enough to separate the transmission torque converter from the engine flywheel/flexplate, then further inspection can be used to isolate the transmission from the engine.

2. While combined with transmission torque converter, if the engine flywheel/flexplate has excessive lateral runout, can produce disturbance.

3. While combined with transmission torque converter, if the engine flywheel/flexplate has excessive lateral runout, can produce disturbance.

4. This step is designed to isolate the transmission from the engine to determine if the disturbance is related to the engine ONLY.

5. Re-position the transmission torque converter to the engine flywheel/flexplate will alter the balance relationship between the torque converter and the engine rear end.

6. Place the J 38792-A sensor onto the underside of the oil pan along the FRONT and the REAR edge allows for a comparison to assist in narrowing down the range of disturbance causes.

7. Engine flywheel/flexplate damage, misalignment and/or imbalance will lead to disturbance.

8. Engine crankshaft balancer that is damaged, misaligned, and/or imbalanced, can produce a disturbance.

Step | Action | Yes | No
--- | --- | --- | ---
Warning: Refer to Work Stall Test Warning in the Preface section.
1 | Are you sent here from the Vibration Analysis - Engine/Accessory Isolation table? | Go to Step 2 | Go to Vibration Analysis - Engine/Accessory Isolation
2 |

1. Raise and support the vehicle. Refer to Lifting and Jacking the Vehicle.
2. Remove the flywheel/flexplate-to-torque converter bolts access cover (if equipped).
3. Determine if clearance enough to separate the transmission torque converter from the engine flywheel/flexplate and secure the torque converter from accidentally engaging with the flywheel/flexplate.

Does the clearance enough to separate the transmission torque converter from engine flywheel/flexplate, and safely secure the torque converter from contacting with engine flywheel/flexplate?

Go to Step 3

Go to Step 9

3 |

1. With the flywheel/flexplate to torque converter access cover removed and vehicle raised, and then mark the relative position between the transmission torque converter and engine flywheel/flexplate.
2. Disconnect the torque converter and move it away from the flywheel/flexplate.
3. Secure the transmission torque converter away from the engine flywheel/flexplate.
4. Lower the vehicle, start the engine and allow the engine to idle.
5. Raise and support the vehicle. Refer to Lifting and Jacking the Vehicle.
6. Visually inspect the flywheel/flexplate for excessive lateral runout.
7. Lower the vehicle.
8. Turn OFF the ignition.

Does the flywheel/flexplate have excessive lateral runout?

Go to Step 6

Go to Step 4

4 |

1. Raise and support the vehicle. Refer to Lifting and Jacking the Vehicle.
2. Inspect the flywheel/flexplate for the following conditions:

• | Loose connection at the engine crankshaft

• | Cracks and/or damage

• | Missing balance weights

Does the flywheel/flexplate exhibit the above listed conditions ?

Go to Step 6

Go to Step 5

5 |

1. With the transmission torque converter still secured away from the engine flywheel/flexplate to avoid accidental engagement with the flywheel/flexplate.
2. Block the front wheels.
3. Apply BOTH the service brake and park brake.
4. With the scan tool and the J 38792-A , Electronic Vibration Analyzer (EVA) 2, still installed, start the engine.
5. Place the transmission in NEUTRAL or PARK.
6. Slowly increase the engine (RPM) to the level at which the disturbance is most noticeable.
7. Record the engine RPM obtained on the scan tool and the most dominant frequency reading if data is obtained from J 38792-A .
8. Turn OFF the ignition.

Does the disturbance significantly reduce or eliminate?

Go to Step 7

Go to Step 9

6 |

1. If the flywheel/flexplate is loose at the engine crankshaft, tighten the flywheel/flexplate mounting bolts according to tightening specification and sequence.
2. If the flywheel/flexplate is cracked, damaged, and/or has missing balance weights, replace the damaged flywheel/flexplate. Refer to following procedures:

• | Engine Flywheel Replacement for the 3.6L (LY7) engine

• | Engine Flywheel Removal for the 4.6L (LH2) engine

Have you finished the tight or replacement operation?

Go to Step 12

--

7 |

1. Raise and support the vehicle. Refer to Lifting and Jacking the Vehicle.
2. Re-fit the transmission torque converter to the engine flywheel/flexplate, 120 degrees away from its original position.
3. Reconnect the transmission torque converter to the engine flywheel/flexplate.
4. Lower the vehicle.
5. Block the front wheels.
6. Apply BOTH the service brake and park brake.
7. Start the engine, with the scan tool J 38792-A still installed.
8. Place the transmission in NEUTRAL or PARK.
9. Slowly increase the engine (RPM) to the level at which the disturbance is most noticeable.
10. Record the engine RPM obtained on the scan tool and the most dominant frequency reading if data is obtained from J 38792-A .
11. If the disturbance is still noticeable, re-position the torque converter to obtain the least amount of disturbance.

Does the disturbance significantly reduce or eliminate?

Go to Step 12

Go to Step 8

8 | Replace the out-of-balance transmission torque converter. Have you finished the replacement? | Go to Step 12 | --
9 |

1. Raise and support the vehicle. Refer to Lifting and Jacking the Vehicle.
2. Place the J 38792-A sensor onto the underside of the oil pan along the FRONT edge.
3. Lower the vehicle.
4. Block the front wheels.
5. Apply BOTH the service brakes and the park brake.
6. Start the engine, with the scan tool and J 38792-A still installed.
7. Place the transmission in NEUTRAL or PARK.
8. Slowly increase the engine (RPM) to the level at which the disturbance is most noticeable.
9. Record the engine RPM obtained on the scan tool and the most dominant frequency reading (if obtained on the J 38792-A from the underside of the engine oil pan).
10. Repeat steps 1 to 9, place the J 38792-A sensor onto the underside of the oil pan along the REAR edge.

Is the disturbance greatest when placing along the engine FRONT edge?

Go to Step 11

Go to Step 10

10 | Replace imbalanced engine flywheel/flexplate. Refer to the following procedures:

• | Engine Flywheel Replacement for the 3.6L (LY7) engine

• | Engine Flywheel Removal for the 4.6L (LH2) engine

Have you finished the replacement?

Go to Step 12

--

11 | Replace the engine crankshaft balancer. Refer to the following procedures:

• | Crankshaft Balancer Replacement for the 3.6L (LY7) engine

• | Crankshaft Balancer Replacement for the 4.6L (LH2) engine

Have you finished the replacement?

Go to Step 12

--

12 |

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

Is the disturbance still present?

Go to Vibration Diagnostic Aids

System OK