GM Service Manual Online
For 1990-2009 cars only

Checks

Causes

DEFINITION: A large engine RPM increase is noted in first gear, Drive range, with little or no vehicle forward speed increase. Second, third, and fourth gear operations are normal. Shifts into first gear are soft or do not occur. First gear ratio is 2.921:1

Forward Clutch

    • Clutch plates worn
    • Porosity in the piston
    • Piston seal damaged
    • Forward clutch housing ball check valve not sealing or damaged
    • Input shaft fluid seals damaged or missing

Control Valve Body Accumulator Assembly

    • Face not flat
    • Spacer plate or gaskets mispositioned or damaged

Input Sun Gear Shaft

Broken shaft

Forward Sprag Clutch Assembly

Sprags not holding

Low Clutch Sprag Assembly

Sprags not holding

Torque Converter Assembly

Stator roller clutch not holding

Line Pressure

Refer to Fluid Pressure High or Low .