GM Service Manual Online
For 1990-2009 cars only

Checks

Causes

Checkball No. 6

Missing

Coast Clutch Plates

Burned, damaged

Coast Clutch Seal/Checkball

Cut, worn or nicked

Lo/Reverse Band

Slipping, burned, damaged

Lo/Reverse Servo Piston

Damaged, seized

Lo/Reverse Servo Seals

Leaking, rolled