GM Service Manual Online
For 1990-2009 cars only
  1. Clean the area thoroughly with solvent.
  2. Remove the torque converter shield, if necessary.
  3. Spray the area with pressurized foot spray powder.
  4. Start the engine, and allow the engine to run at a fast idle.
  5. Drive the vehicle approximately 24 km (15 miles), or until the vehicle reaches an operating temperature of 88°C (190°F).
  6. With the engine running, inspect the transmission for leaks.
  7. Turn the engine to the OFF position, and inspect the transmission for leaks caused by drainback.
  8. Proceed with the following procedure if no leaks are identified:
  9. • Identify the type of oil. (Transmission fluid contains a red dye.)
    • Determine the source of the leak. The air stream generally carries leaking oil toward the rear of the vehicle by the air stream.
  10. Repair the leaks.
  11. Inspect the transmission again as necessary.

The following components are possible locations of transmission oil leaks:

  1. The transmission pan
  2. The following conditions may cause a leak in the transmission pan:

    • Attaching bolts that are not correctly torqued
    • An improperly installed or damaged gasket
    • The oil pan mounting face is not flat
  3. The case
  4. The following components may cause a case leak:

    • Servo cover porosity or O-ring damage
    • A missing or damaged filler pipe multi-lip seal
    • A missing or misplaced filler pipe bracket
    • A damaged electrical connector O-ring
    • A damaged manual shift seal
    • Loose or damaged oil cooler connector fittings
    • A damaged vacuum modulator O-ring.
    • Damaged or worn output shaft seals
    • A loose line-pressure plug
    • A damaged transmission oil pan gasket
    • A porous casting
  5. The converter end
  6. The following conditions may cause a converter end leak:

    • Converter seal damage
    • The following conditions cause converter seal damage:
       - A seal lip cut (Check the converter hub for damage.)
       - A bushing moved forward and damaged
       - A garter spring missing from the seal
    • A converter leak in the weld area
    • A porous casting
    • A worn or damaged turbine shaft oil seal
  7. The vent pipe
  8. The following conditions may cause a leak at the vent pipe:

    • Overfilling
    • Water in the fluid
    • A porous case
    • An incorrect fluid level indicator
    • Plugged drain-back holes