GM Service Manual Online
For 1990-2009 cars only

The cause of most external leaks can be located and repaired with the transmission in the vehicle. There are three methods for locating automatic transmission fluid leaks.

General Method

  1. Verify that the leak is transmission fluid.
  2. Thoroughly clean the suspected leak area.
  3. Drive the vehicle for 24 km (15 miles) or until normal operating temperatures are reached.
  4. Park the vehicle over clean paper or cardboard.
  5. Turn the ignition switch off.
  6. Wait approximately 30 minutes.
  7. Inspect the paper for spots in proportion to its position under the transmission assembly.
  8. Make the necessary repairs.

Powder Method

  1. Thoroughly clean the suspected leak area with solvent.
  2. Apply an aerosol powder or baby powder to the suspected leak area.
  3. Drive the vehicle for 24 km (15 miles) or until the normal operating temperatures are reached.
  4. Turn the ignition switch off.
  5. Inspect the suspected leak area and trace the leak path through the powder to find the source.
  6. Make the necessary repairs.

Dye and Black Light Method

Tools Required

    • J 28428-E High Intensity Black Light
    • J 28431-6 Florescent Oil Additive
  1. Add 30 ml (1 oz.) of J 28431-6 into the automatic transmission fluid filler tube.
  2. Drive the vehicle for 24 km (15 miles) or until normal operating temperatures are reached.
  3. Turn the ignition switch off.
  4. Use a J 28428-E in order to locate the source of the leak.
  5. Make the necessary repairs.