GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Generic 🢒 2003 🢒 Unit Repair 🢒 Transmission/Transaxle 🢒 Automatic Transmission - MU6 🢒 Road Test

Important: 

   • Perform the road test following the sequence given.
   • Km/h (mph) shift points will vary with actual throttle position and driver habits
   • Compare the results of the road test with the Transaxle Shift Speed Schedule. Use these results with the diagnosis information in this section for the transaxle evaluation.
   • This test should only be performed when traffic and road conditions permit.
   • Observe all traffic and safety regulations.

Drive and Reverse Engagement Test
  1. Turn the ignition switch to ON.
  2. Depress the brake pedal fully.
  3. Place the manual selector in the Park (P) range.
  4. Start the engine.
  5. Move the manual selector from the Park (P) range to the Reverse (R) range.
  6. Observe the reverse engagement.
  7. Move the manual selector from the Reverse (R) range to the Drive (D) range.
  8. Observe the drive engagement.
  9. Move the manual selector from the Drive (D) range to the Park (P) range.
  10. Turn the ignition switch to the LOCK position.
  11. Verify that the following conditions exist:
    12. • The reverse engagement takes approximately 1.4 seconds at the normal operating fluid temperature. If transaxle is cold run for 10 minutes to bring to proper temperature.
    • Normal operating fluid temperature is 70-80°C (158-176°F).
    • The drive engagement from the reverse engagement takes approximately 1.0 seconds.
    • The reverse and the drive engagements should be immediate, but not harsh.
    • If the reverse and the drive engagements are slow to engage or seem too harsh, refer to Line Pressure Check .

Upshifts and Torque Converter Clutch (TCC) Apply Test
  1. Move the manual selector to the Drive (D) range.
  2. Depress the Overdrive Switch.
  3. Accelerate the vehicle using steadily increasing throttle pressure.
  4. Note the vehicle speeds and the shift points for the following gears:
    5. • Second gear (2)
    • Third gear (3)
    • Overdrive (4)
    • Observe the vehicle speeds and the shift points at which the Torque Converter Clutch (TCC) engages. TCC apply should occur in 3rd gear.

Part Throttle Downshift Test

Important: The TCC will not apply and the 4th gear upshift is delayed until the engine coolant temperature has reached at least 55°C (131°F).

  1. Operate the vehicle at the speeds of 64-88 km/h (40-55 mph).
  2. Verify that the manual selector is in the Drive (D) range and the Overdrive (Overdrive) switch is depressed.
  3. Quickly press the accelerator pedal to approximately half throttle.
  4. Verify that the TCC releases.
  5. Verify that the transaxle immediately downshifts to third gear.

Full Throttle Downshift Test
  1. Operate the vehicle at the speeds of 77-88 km/h (48-55 mph).
  2. Verify that the manual selector is in the Drive (D) range and the Overdrive switch is depressed.
  3. Quickly press the accelerator pedal to the Wide Open Throttle (WOT) position.
  4. Verify that the TCC releases.
  5. Verify that the transaxle immediately downshifts to second gear.

Manual Downshift Test
  1. Move the manual selector to the Drive (D) selector.
  2. Operate the vehicle at 64-88 km/h (40-55 mph) and the Overdrive switch pressed.
  3. Release the accelerator pedal and the Overdrive Switch.
  4. Verify the following operating conditions:
    5. • The Torque Converter Clutch (TCC) releases.
    • The transaxle downshifts immediately to third gear.
    • The engine reduces the vehicles speed.
  5. Operate the vehicle at 48 km/h (30 mph).
  6. Release the accelerator pedal.
  7. Move the manual selector to the Second (2) range.
  8. Verify the following operating conditions:
    9. • The TCC at 15 mph.
    • The transaxle downshifts immediately to second gear.
    • The engine reduces the vehicles speed.
    • Manual 2nd to low shift.
  9. Move the manual selector to the Drive (D) selector.
  10. Operate the vehicle at 24 km/h (15 mph).
  11. Release the accelerator pedal.
  12. Move the manual selector to the Low (L) range.
  13. Verify the following operating conditions:
    14. • The TCC releases.
    • The transaxle downshifts immediately to first gear.
    • The engine reduces the vehicles speed.

Coastdown Downshift Test
  1. Verify the manual selector is in the Drive (D) position and the Overdrive switch is depressed.
  2. Depress the accelerator pedal until the transaxle is in 4th gear.
  3. Release the accelerator pedal.
  4. Lightly apply the brake pedal.
  5. Observe the TCC release.
  6. Observe the vehicle speeds at points of downshifts.

Manual Third (D) Gear Range Selection Test
  1. Stop the vehicle.
  2. Move the manual selector to the Drive (D) range.
  3. Slowly accelerate the vehicle and verify the following operating conditions:
    4. • The transaxle upshifts from the first gear to the second gear.
    • The transaxle upshifts from the second gear to the third gear.

Manual Second (2) Range
  1. Stop the vehicle.
  2. Place the manual selector in the second (2) range.
  3. Slowly accelerate the vehicle to 40 km/h (25 mph).
  4. Verify that the transaxle upshifts from the first gear to the second gear.
  5. Verify that the transaxle does not upshift from second gear to third gear.
  6. Verify that the Torque Converter Clutch (TCC) does not engage.

Manual Low Test
  1. Stop the vehicle.
  2. Place the manual selector in the Low (L) range.
  3. Slowly accelerate the vehicle.
  4. Verify that the transaxle does not upshift from the first gear to the second gear.
  5. Verify that the Torque Converter Clutch (TCC) does not engage.

Reverse (R) Test
  1. Stop the vehicle.
  2. Place the manual selector in the Reverse (R) range.
  3. Slowly accelerate the vehicle.
  4. Verify that the vehicle operates in a rearward direction.