Line Pressure Too Low
WARNING: This page does not describe the selected car, but rather 124 other vehicles, including the 1991 Chevrolet Pickup, 1991 Chevrolet Cab & Chassis, 1988 GMC Vandura Special, 1988 GMC Vandura, and 1988 GMC Value Van. However, it is still accessible from the selected car via links, so may be relevant.
- Transmission fluid level low, faulty vacuum modulator assembly. Filter blocked or restricted, "O" ring on filter intake pipe omitted or damaged, intake pipe split or leaking, or incorrect filter.
- Pump assembly damaged, worn, or mismatched parts. Pump gear clearance damaged or worn. Pressure regulator spring too weak or not enough spacers in pressure regulator.
- Internal leak in direct clutch circuit (pressure normal in Neutral, Low, Intermediate and Drive, but low in Reverse). Internal leak in forward clutch circuit (pressure normal in Neutral and Reverse, low in Drive).
- Case assembly porous in intake bore area. Missing plug or leak at intermediate clutch plug. Low-Reverse check ball installed wrong or missing (causing loss of Reverse and no engine braking in low).