GM Service Manual Online
For 1990-2009 cars only

First Gear Only

Checks

Cause

DEFINITION: The transmission only provides first gear in Drive range. The vehicle accelerates from a stop in first gear and does not upshift. First gear ratio is 2.921:1.

Control Valve Body Assembly

    • The 1-2 shift valve (318) is stuck or binding.
    • Debris is found in the control valve body (301) or the control valve body spacer plate and gasket assembly (396)
    • The spacer plate and gaskets (369-371) are misassembled.

Second Clutch Assembly

    • A missing or not seated second clutch backing plate retaining ring (627)
    • A missing or misassembled second clutch backing plate (626)
    • Worn, damaged, or misassembled clutch plates (623-625)
    • A missing or not seated second clutch spring retaining ring (622)
    • A damaged spring assembly (621) or piston (620)
    • A missing or damaged second clutch housing ball check valve assembly (618)
    • A damaged second clutch housing assembly (617)

Reverse Reaction Drum

Damaged splines of the reverse reaction drum (669)