GM Service Manual Online
For 1990-2009 cars only

Checks

Cause

Intermediate Servo (128-137)

    â€¢ The apply pin is wrong or is sticking (129)
    â€¢ The seals are cut, are damaged, or are missing (128, 132, 134)
    â€¢ The piston is sticking or is damaged (133)
    â€¢ Porosity is in the case servo bore (15)

Accumulator Exhaust Valve (125-126)

The valve is sticking, not seating

Control Valve Assembly

The 1-2 shift valve is sticking (320)

Spacer Plate (20)

    â€¢ The gaskets are incorrectly installed (19)
    â€¢ The governor feed to the 1-2 shift valve is blocked
    â€¢ The intermediate band apply feed orifice is blocked (15, 137)
    â€¢ Wrong spacer plate

Case (15)

The intermediate servo apply passage (second oil) is blocked

Case Cover (40)

The intermediate servo apply passage (second oil) is blocked

Intermediate Band (606)

    â€¢ The band is improperly installed
    â€¢ The band is burned or broken