Gearboxes & Transmissions
About Gearboxes & Transmissions
A transmission is the gearbox that gives the engine its range of ratios, and the listings here are for the complete unit and its major assemblies. The samples show complete 5-speed and 6-speed overdrive assemblies, 6-speed and 7-speed gear sets, top covers and hardware kits, mostly for Harley-Davidson models. Riders shop here for a damaged transmission, a change in the number of speeds, or a restoration.
A complete transmission assembly replaces the gearbox as a unit, while a gear set replaces the gears inside your existing cases. The 31 listings are model specific, such as 5-speed assemblies for 1970 to early 1984 Harley-Davidson models, a 6-speed overdrive assembly for 1991 to 1999 Softails, and M8 top cover kits for 2017 to 2024 touring models. Check the year range and the number of speeds before you order. A different number of speeds can need matching parts, so read the maker's notes. Fit new gaskets and seals, check the bearings and clutch, and fill with the fluid your manual specifies.
Brands here include Colony, Jims, HardDrive, Baker Drivetrain and Gardner-Westcott. Pick your machine in the Ride Finder at the top of the page. For the smaller parts see Gearbox & Transmission Parts, Bearings and Gaskets & Seals, all part of Transmission & Drivetrain.
FAQs on motorcycle gearboxes and transmissions
What is the difference between a complete transmission and a gear set?
A complete transmission assembly replaces the gearbox as a unit, with its shafts and gears already assembled. A gear set replaces the gears inside your existing cases, which means the gearbox has to be opened and rebuilt. Check which one a listing offers.
What fluid does a motorcycle transmission use?
It depends on the bike. Some share the engine oil, and others have separate gearbox oil, with a grade and quantity given in the service manual. Use exactly what your manual specifies and fill to the stated level.
What should I replace when the transmission is out?
Fit new gaskets, seals and fasteners that the manual says are single use, and inspect the bearings, the clutch and the shift parts. Replace anything outside limits, since a worn bearing can damage a new gear set.
Is replacing a transmission a home job?
It is an advanced job. It needs the transmission removed and fitted with the right tools, and often the clutch and primary opened. Follow your service manual, or have a shop do it if you are not sure.
