GM Service Manual Online
For 1990-2009 cars only

Purpose/Description Of Test

A stall test is preformed to inspect the overall performance of the automatic transmission and engine assembly by measuring the stall speed in both the DRIVE and REVERSE gear ranges.

Conditions

    • Verify that the automatic transmission fluid (ATF) temperature is between 50-80°C (120-176°F).
    • All additional electrical loads are OFF.

Notice: Do not continuously run the test procedure for longer than 5 seconds because of the extreme increase in the automatic transmission fluid (ATF) temperature. Also, be sure to keep the interval between stall tests to more than 1 minute in order to prevent damage to the automatic transmission internal components.

Procedure

  1. Chock all 4 wheels and fully apply the parking brake in order to prevent any vehicle movement during testing.
  2. Apply firm pressure to the service brake pedal with the left foot in order to apply the service brakes.
  3. Move the automatic transmission manual gearshift selector from the PARK position to the DRIVE position.
  4. Evenly press the accelerator pedal to the wide-open throttle (WOT) position with the right foot.
  5. Record the maximum engine RPM noted within 5 seconds of achieving the WOT position, and then return to the closed throttle position. Return the gear selector to the PARK position.
  6. Wait 1 minute before proceeding to the next portion of the test procedure.
  7. Move the automatic transmission manual gearshift selector from the PARK position to the REVERSE position.
  8. Evenly press the accelerator pedal to the wide-open throttle (WOT) position with the right foot.
  9. Record the maximum engine RPM noted within 5 seconds of achieving the WOT position, and then return to the closed throttle position. Return the gear selector to the PARK position.
  10. Specifications
    2,450-2,750 RPM

Stall Test Results

Result

Possible Cause

Observed RPM is LOWER than the specification in BOTH DRIVE AND REVERSE ranges

    • Base engine concern
    • Torque converter clutch (TCC) internal one-way clutch failure

Observed RPM is HIGHER than the specification in DRIVE ONLY

    • Line pressure is below specifications
    • Forward clutch (565) concern
    • Front internal gear and low clutch sprag assembly (25) concern

Observed RPM is HIGHER than the specification in REVERSE ONLY

    • Line pressure is below specifications
    • Direct clutch (562) slipping
    • Low and reverse clutch (511) slipping

Observed RPM is HIGHER than the specification in BOTH DRIVE AND REVERSE ranges

    • Line pressure is below specifications
    • 1-2 reverse clutch (603) slipping
    • Internal fluid leak concern in each of the selected ranges