GM Service Manual Online
For 1990-2009 cars only

Flush the oil cooler lines following a breakdown of the transmission in order to eliminate contaminated oil. This helps prevent trouble after repairs of the transmission.

  1. Disconnect the oil cooler lines at the transmission case.
  2. If an auxiliary filter has been installed, disconnect the oil cooler return line a the auxiliary filter instead of the transmission.
  3. Notice: Do not exceed 689 kPa (100 psi) air pressure or damage may result to the oil cooler.

  4. Back flush the oil cooler and lines using clean mineral spirits and compressed air.
  5. Flush all remaining mineral spirits from the oil cooler and lines using compressed air.
  6. Flush the oil cooler lines again with transmission oil.
  7. 5.1. Test the oil cooler for free flow of oil.
    5.2. If the flow of oil is restricted, replace the tank and cooler assembly.
    5.3. If debris from the oil cooler circuit persists, install a new auxiliary filter in the oil return line between the oil cooler and the transmission.