Flexplate/Torque Converter Vibration Test (8.1L)

WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

To determine and correct a torque converter vibration, use the following general procedure to achieve the best possible torque converter-to-flywheel balance. Refer to Transmission Replacement (With 6.6L Engine) or Transmission Replacement (With 8.1L (L18) Engine) for detailed procedure steps as appropriate.

CAUTION: Refer to Battery Disconnect Caution in Cautions and Notices.

Disconnect the battery.
Raise the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.
Remove the starter motor bolts and position the starter motor aside. Refer to Starter Motor Replacement (4.3L Engine) or Starter Motor Replacement (4.8L, 5.3L, and 6.0L Engines) or Starter Motor Replacement (6.6L (LB7) Engine) or Starter Motor Replacement (6.6L (LLY) Engine) or Starter Motor Replacement (8.1L Engine) in Engine Electrical.

Fig 1: Converter Housing Inspection Cover (With 8.1L (L18) Engine)

Courtesy of GENERAL MOTORS CORP.

Remove the converter housing inspection cover.
Repeat this procedure until you obtain the best possible balance.
- Unless already removed, remove the starter motor bolts and position the starter motor aside. Refer to Starter Motor Replacement (4.3L Engine) or Starter Motor Replacement (4.8L, 5.3L, and 6.0L Engines) or Starter Motor Replacement (6.6L (LB7) Engine) or Starter Motor Replacement (6.6L (LLY) Engine) or Starter Motor Replacement (8.1L Engine) in Engine Electrical.
- Remove the torque converter bolts.
- Rotate the torque converter one bolt position.
- Install the torque converter bolts.
  Tighten: Tighten the bolts to 60 N.m (44 lb ft).
- Install the starter motor and starter motor bolts. Refer to Starter Motor Replacement (4.3L Engine) or Starter Motor Replacement (4.8L, 5.3L, and 6.0L Engines) or Starter Motor Replacement (6.6L (LB7) Engine) or Starter Motor Replacement (6.6L (LLY) Engine) or Starter Motor Replacement (8.1L Engine) in Engine Electrical.
- Connect the battery.
- Start the vehicle and test for vibration again.

CAUTION: Refer to Battery Disconnect Caution in Cautions and Notices.

Disconnect the battery.
Raise the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.
Remove the starter motor bolts and position the starter motor aside. Refer to Starter Motor Replacement (4.3L Engine) or Starter Motor Replacement (4.8L, 5.3L, and 6.0L Engines) or Starter Motor Replacement (6.6L (LB7) Engine) or Starter Motor Replacement (6.6L (LLY) Engine) or Starter Motor Replacement (8.1L Engine) in Engine Electrical.
Install the converter housing inspection cover.
Install the starter motor and starter motor bolts. Refer to Starter Motor Replacement (4.3L Engine) or Starter Motor Replacement (4.8L, 5.3L, and 6.0L Engines) or Starter Motor Replacement (6.6L (LB7) Engine) or Starter Motor Replacement (6.6L (LLY) Engine) or Starter Motor Replacement (8.1L Engine) in Engine Electrical.
Lower the vehicle.

CAUTION: Refer to Battery Disconnect Caution in Cautions and Notices.

Connect the battery.