GM Service Manual Online
For 1990-2009 cars only

Harsh Neutral to Reverse or Harsh Neutral to Drive

Checks

Cause

Modulator or Lines

Loss of vacuum due to damaged lines or modulator

Reverse Servo Cushion Spring

Broken or wrong spring

Control Valve Assembly

    • Missing #5 checkball, results in harsh reverse
    • Missing #6 checkball, results in harsh drive

Forward Servo Cushion Spring

Broken or wrong spring

Spacer Plate

Thermal element does not close when the element is warm, causing harsh Neutral to Drive