GM Service Manual Online
For 1990-2009 cars only

Tools Required

    • J 28431-6 Fluorescent Oil Dye - 6 1 oz
    • J 42220 Universal 12V Leak Detection Lamp

Dye and Black Light Method

Use the J 42220 and the J 28431-6 to isolate the leak point. Fluid dye and black light kits are also available from various tool manufacturers. All transmissions that are diagnosed, that require replacement due to leakage, must be diagnosed with the leak dye and black light method.

  1. Follow the manufacturer's instructions in order to determine the amount of dye to use.
  2. Detect the leak with the black light.
  3. Make the necessary repairs.

General Method

  1. Verify that the leak is transmission fluid.
  2. Thoroughly clean the suspected leak area.
  3. Operate the vehicle for 24 km (15 mi), or until normal operating temperatures are reached.
  4. Park the vehicle over clean paper or cardboard.
  5. Shut OFF the engine.
  6. Look for fluid spots on the paper.
  7. Make the necessary repairs.

Powder Method

  1. Thoroughly clean the suspected leak area with solvent.
  2. Apply an aerosol type powder, such as foot powder, to the suspected leak area.
  3. Operate the vehicle for 24 km (15 mi), or until normal operating temperatures are reached.
  4. Shut OFF the engine.
  5. Inspect the suspected leak area.
  6. Trace the leak path through the powder in order to find the source of the leak.
  7. Make the necessary repairs.

Find the Cause of the Leak

Pinpoint the leak and trace the leak back to the source. You must determine the cause of the leak in order to repair the leak properly. For example, if you replace a gasket, but the sealing flange is bent, the new gasket will not repair the leak. You must also repair the bent flange. Before you attempt to repair a leak, check for the following conditions, and make repairs as necessary:

Gaskets

    • Fluid level/pressure is too high
    • Plugged vent or drain-back holes
    • Improperly tightened fasteners
    • Dirty or damaged threads
    • Warped flanges or sealing surface
    • Scratches, burrs, or other damage to the sealing surface
    • Damaged or worn gasket
    • Cracking or porosity of the component
    • Improper sealant used, where applicable
    • Incorrect gasket

Seals

    • Fluid level/pressure is too high
    • Plugged vent or drain-back holes
    • Damaged seal bore
    • Damaged or worn seal
    • Improper installation
    • Cracks in component
    • Manual or output shaft surface is scratched, nicked, or damaged
    • Loose or worn bearing causing excess seal wear