How to Perform an Automatic Transmission Flush at Home

by Editorial Team

If you have an automatic transmission in your vehicle then you should have the transmission fluid flushed to keep your vehicle well maintained. The transmission is often forgotten until problems arise. By then it is too late and you end up with costly repairs. It is best to flush the transmission fluid every 30,000 miles or three years. More often if the vehicle is used for towing. Most auto repair shops want you to believe that you have to use their expensive machine to flush your automatic transmission fluid. This article will show you how to do it at home with a few simple tools.

Step 1

Get everything you need ready before you start the transmission flush service. Once you start you don't need to stop until you are finished. Run the vehicle until it gets to normal operating temperature and then turn it off. Raise the front of the vehicle with the jack and place it on jack stands. Now you will need to find where the transmission cooler lines go into the radiator. They may either be on the sides or on the bottom of the radiator. Place the 5 gallon bucket under where the transmission cooler lines go into the radiator.

Step 2

Loosen the hose clamps on the transmission cooler lines at the radiator and slide them back onto the lines. Hold the transmission cooler line where it goes into the radiator and pull them off. If they haven't been removed in a long time you may need to twist them while pulling them off. Once you have both transmission cooler lines removed and in the bucket remove the transmission dipstick and place the long funnel into the tube.

Step 3

Open the case of transmission fluid and remove the caps from all of the transmission fluid. Once you start the vehicle it will start pumping the transmission fluid out into the 5 gallon bucket. You will need to add fluid quickly. Start the vehicle (or have your helper do it) and then start adding transmission fluid through the funnel. Pour the transmission fluid quickly, and try not to let the funnel run dry. Pour 9 of the 12 quarts of transmission fluid into the funnel and then shut the vehicle off. You want to leave about 3 quarts available in case you need to top off the transmission fluid.

Step 4

Now replace the transmission cooler lines and remove the vehicle from the jack stands and lower it back to the ground. Start the vehicle and make sure it is up to normal operating temperature. With your foot on the brake pedal move the vehicle through all of the gears several times and then place it back in park. Now insert the dipstick and check the fluid level. If it is within the normal range then you have completed the transmission flush service. If you need to add more fluid; add about half a quart at a time and then run the vehicle through the gears again and recheck the level. Do this until the level is within the normal range. If you have too much fluid then you will need to drain some of it until it is within the normal range. Shut the vehicle off and locate the drain plug and let a little fluid out. Replace the drain plug and then start the vehicle and check the fluid level again.

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