GM Service Manual Online
For 1990-2009 cars only

A noise or vibration that is noticeable when the vehicle is in motion MAY NOT be the result of the transmission.

If noise or vibration is noticeable in PARK and NEUTRAL with the engine at idle, but is less noticeable as RPM increases, the vibration may be a result of poor engine performance.

    • Vibration may also be caused by a small amount of water inside the converter.
    • Inspect the engine and transmission mounts for damage and loose bolts.
    • Inspect the transmission case mounting holes for the following conditions:
       - Missing bolts, nuts, and studs
       - Stripped threads
       - Cracks
    • Inspect the flywheel for the following conditions:
       - Missing or loose bolts
       - Cracks
       - Imbalance
    • Inspect the torque converter for the following conditions:
       - Missing or loose bolts or lugs
       - Missing or loose balance weights
       - Imbalance caused by heat distortion or fluid contamination
    • If the noise or vibration is noticeable in PARK and NEUTRAL with the engine at idle, but is more noticeable as RPM increases, the vibration may be an engine imbalance or a transmission imbalance. Refer to Torque Converter Diagnosis.