- Inspect the engine flywheel and the torque converter for loose
or missing torque converter-to-engine flywheel bolts. Tighten or replace the
 bolts as necessary. Refer to 
Engine Flywheel Replacement 
 and/or 
Flywheel to Torque Converter Bolt Replacement 
  in Automatic Transaxle -
4T60-E.
 
- Inspect the torque converter for damaged or missing balance weights.
Replace the torque converter if the torque converter is damaged or if any
 balance weights are missing.
 
- Change the position of the torque converter to the engine flywheel
120 degrees at a time in order to cancel out an engine and torque converter
 imbalance. Check for vibration improvements in each position.
 
Important: Check to make sure that the engine flywheel-to-torque converter bolts
do not bottom in the holes. Rotate the torque converter by hand after adding
 the washers.
- If the unbalanced condition continues, leave the torque converter bolted
to the engine flywheel in the best balanced position. Install longer engine
 flywheel-to-torque converter bolts and add or remove washers in order to
achieve  the best balance.