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How to Remove Water From a Transmission

by Jack Hathcoat

Water inside of an automatic transmission is highly destructive. If left unaddressed, the friction plates in the transmission will separate and the transmission will no longer shift into any gears. The only option is to quickly service and flush the transmission with new transmission fluid, and in some cases -- especially if the transmission is large and used behind a V-8 engine -- this process will require several dozen quarts of fluid.

Jack up the vehicle and place jack stands under the frame. Lower the vehicle onto the stands and use a socket wrench to remove the transmission service pan. Allow the transmission to drain as much of the milky fluid that is contaminated with water as possible. Remove the transmission filter, if accessible, as well.

Spray the old filter with aerosol brake cleaner and reinstall it. Clean the old gasket off of the transmission pan with a gasket scraper, install a new gasket and reinstall the transmission pan.

Raise the hood of the car and remove the lower transmission oil cooler line that goes to the radiator. Place a section of rubber hose over the line and route the line to a drain pan. Add five to seven quarts of new fluid to the transmission, based on the manufacturer's service recommendations.

Start the engine and allow it to run for several minutes while judging the amount of transmission fluid that is discharged into the drain pan. When five to seven quarts of fluid are discharged, shut the engine off and add additional fluid to the transmission. Continue this process until the fluid that is discharged is no longer milky.

Reinstall the lower transmission cooler line. Remove the transmission service pan and replace the old transmission filter with a new one. Reinstall the transmission pan. Fill the transmission with the recommended amount of new transmission fluid. Remove the jack stands and lower the car.

Warning

  • If the transmission is contaminated for any length of time by water intrusion, service is not likely to do much good. A complete rebuild to replace the friction plates is required.

Items you will need

About the Author

Jack Hathcoat has been a technical writer since 1974. His work includes instruction manuals, lesson plans, technical brochures and service bulletins for the U.S. military, aerospace industries and research companies. Hathcoat is an accredited technical instructor through Kent State University and certified in automotive service excellence.

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