GM Service Manual Online
For 1990-2009 cars only

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 leak tracing 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.

Dye and Black Light Method

A fluid dye and black light kit is available from various tool manufacturers.

  1. Follow the manufacturer's instructions in order to determine the amount of dye to use.
  2. Operate the vehicle for 24 km (15 mi) or until normal operating temperatures are reached.
  3. Detect the leak with the black light.
  4. 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 shaft or output shaft surface is scratched, nicked, or damaged
    • Loose or worn bearing causing excess seal wear

Possible Points of Fluid Leaks

Transmission Case Cover and/or Valve Body Cover

    • Incorrectly tightened bolts
    • Improperly installed or damaged gasket/seal
    • Damaged mounting face
    • Incorrect gasket seal

Case Leak

    • Damaged input speed sensor seal
    • Damaged manual shaft seal
    • Loose or damaged oil cooler lines/seals
    • Worn or damaged axle shaft oil seal
    • Loose line pressure pipe plug or fluid level pipe plug
    • Porous casting
    • Warped torque converter housing
    • Damaged converter housing to case seal

Leak at the Torque Converter End

    • Converter leak in the weld area
    • Converter seal lip cut. Check the converter hub for damage
    • Converter seal bushing moved forward and damaged
    • Converter seal garter spring missing from the seal
    • Porous casting of the torque converter housing

Leak at the Vent

    • Overfilled system
    • Water or coolant in the fluid; The fluid will appear milky
    • Transmission case porous
    • Incorrect fluid level indicator causing an overfilled system
    • Plugged vent

Leak Inspection Points


Object Number: 2178032  Size: LF
(1)Manual Shift Shaft Seal
(2)Auxiliary Pump Press Plug
(3)Control Valve Body Cover Wiring Connector Hole Seal
(4)Drive Motor/Generator Power Inverter Module Cable Assembly Seal - 3 Phase
(5)A/Trans Vent Assembly
(6)Transmission Fluid Filler Tube Seal
(7)Pump Wiring Harness Connector Seal
(8)Torque Dampener and Differential Housing Assembly to Case Joint
(9)Front Wheel Drive Shaft Oil Seal Assembly (LHS)
(10)Oil Level Plug
(11)A/Trans Fluid Pump Seal
(12)A/Trans Torque Dampener Assembly
(13)Front Wheel Drive Shaft Oil Seal Assembly (RHS)
(14)Control Valve Body Cover Gasket
(15)Transmission Fluid Drain Plug
(16)A/Trans Case Cover Gasket