GM Service Manual Online
For 1990-2009 cars only

Slipping 1-2 Upshift

Checks

Cause

Oil Pressure

Low

Valve Body Checkball

Dropped out

2nd Clutch Piston Seals

Leak

2nd Clutch Piston Checkball

Stuck open

2nd Clutch Piston Seals

Cracked or broken

2nd Clutch Plates

Worn

Oil Pump Hub Seal Rings

Leak