How to Flush Automatic Transmission Fluid

by Allen Moore

Prior to the invention of the automatic transmission flush machine, a transmission service was nothing more than removing the pan, replacing the filter, reinstalling the pan and adding five or six quarts of fluid back into the transmission. While this was better than ignoring your transmission altogether, it really only allowed for the replacement of 30 percent of the transmission fluid. Fortunately, transmission flush machines do exist, and they’re in the hands of trained transmission technicians.


Fill a 5-gallon bucket with the recommended amount of transmission fluid for your vehicle. Make sure to use the fluid specified by your vehicle’s manufacturer for your type of transmission.


Insert the suction hose from the automatic transmission flush machine into the bucket and turn the machine on to the "Fill" setting. Fill the machine and shut it off when done.


Disconnect the transmission cooler lines from the transmission with a box wrench. Attach the suction and discharge hoses from the flush machine to the cooler lines with a socket set.


Start the vehicle and turn the flush machine to the "Flush" setting. Wait for the new transmission fluid to empty into the transmission. Shut the machine and the vehicle off.


Remove the suction and discharge hoses from the cooler lines with the socket set. Reconnect the cooler lines to the transmission cooler with the box wrench.


  • close Do not attempt this job unless you’re a trained automotive transmission technician or serious damage to the transmission may occur.

Items you will need


About the Author

Allen Moore's career includes awards in poetry and creative fiction, published lyrics, fiction books and nonfiction articles as well as a master certification in automotive service from the Ford Motor Company. Moore is a contributing writer for and various other websites, a ghostwriter for Rainbow Writing and has over a dozen works of fiction currently in print.

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