GM Service Manual Online
For 1990-2009 cars only

1st Gear Range Only - No Upshift

Checks

Causes

Control Valve Body (60)

    â€¢ The 1-2 Shift valve is sticking
    â€¢ The spacer plate or gaskets are mispositioned or damaged

Case (103)

The case to valve body face is damaged or is not flat

Shift Solenoid Valves (366/368)

    â€¢ Stuck or damaged
    â€¢ Faulty electrical connection

2-4 Servo Assembly (13-28)

    â€¢ The apply passage case is restricted or blocked
    â€¢ Nicks or burrs on the servo pin or on the pin bore in the case
    â€¢ Fourth servo piston is installed backwards

2-4 Band Assembly (602)

    â€¢ The 2-4 band is worn or damaged
    â€¢ The band anchor pin is not engaged