How to Change a Harley's Transmission Oil

by Chris Gilliland

While most motorcyclists are well-versed in the proper method to replace their machine's motor oil, Harley-Davidson riders must also replace a separate fluid that lubricates their motorcycle's transmission. This can cause some confusion for newer owners of Milwaukee's finest motorcycles, since most manufacturers consolidate their motor and transmission into one single unit. Luckily, changing the transmission fluid is a simple task that doesn't require special knowledge.

Unscrew the filler cap from the right side of the transmission. Locate the drain plug on the bottom of the transmission and place an oil pan directly beneath it.

Unscrew the drain plug using a socket wrench and allow the transmission fluid to drain completely.

Remove the O-ring from the drain plug and wipe away any debris or buildup with a shop towel. Slip a new O-ring onto the drain plug. Insert the drain plug into the transmission and tighten it with a socket wrench. Wipe away any remaining fluid from the bottom of the transmission with a shop towel.

Insert a funnel into the filler neck on the right side of the transmission. Add up to one quart of fresh transmission fluid. Remove the funnel and wipe away any transmission fluid that may have spilled with a shop towel. Screw the filler cap onto the filler neck.


  • check Warm the transmission fluid first to speed up the process. Start the motorcycle and let it idle for five minutes to warm the fluids, then stop the motor. Be careful when removing the drain plug since the motor, transmission, and exhaust pipes may be hot.


  • close Don't over tighten the drain plug. The threads that secure the drain plug to the transmission can be damaged easily by excessive torque.

Items you will need


About the Author

An avid motorcyclist, Chris Gilliland has immersed himself into the two-wheeled world while balancing work life and raising three daughters. When he is not managing the parts department of a local, multi-line motorcycle dealership, Gilliland can often be found riding, writing or working on his motorcycle blog, Wingman's Garage.

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  • photo_camera socket set wrench image by Christopher Dodge from