Your Harley-Davidson’s transmission is one of three separate components that drive your motorcycle forward. Like the motor and primary drive, the transmission uses it own fluid to lubricate the collection of gears within it. As time wears on, the oil begins to break down and lose its ability to reduce friction. If left unchanged, the transmission’s gears will fail as friction continues to build. Harley-Davidson recommends changing the transmission’s gear oil every 2,500 miles to extend your motorcycle’s service life.
1. Unscrew the drain plug from the bottom of the transmission, using a 5/8-inch socket and a socket wrench. Drain the transmission fluid into an oil pan.
2. Clean the drain plug’s threads and tip with a shop towel. Pull the rubber O-ring off the drain plug and replace it with a new one. Screw the drain plug into the transmission and tighten it to 21 foot-pounds, using a torque wrench.
3. Unscrew the transmission’s oil cap from the right side of the motorcycle. Insert a funnel into the transmission’s filler neck
4. Fill the transmission with up to 1 qt.of 75W90 transmission oil. Remove the funnel and wipe away any spills with a shop towel. Screw the filler cap into place.