Gearbox & Transmission Parts
About Gearbox & Transmission Parts
Gearbox parts are the gears, shafts, shifter parts and small hardware inside the transmission. Riders shop here when a gear is chipped, a bike jumps out of gear or misses shifts, or when they are rebuilding a gearbox or fitting a gear set.
The samples are mostly for Harley-Davidson V-twins, including main shaft and countershaft gears, direct drive and overdrive gear sets in 6-speed form, thrust washers, snap rings, a shift pawl and shift rod extension, and a transmission cover. Gears are specific to the shaft, tooth count and year range, so match the listing exactly. In a direct drive gear set, top gear turns the output at the same speed as the engine, and an overdrive top gear turns the engine slower for the same road speed.
Gears that mesh wear together, so renew mating gears as a pair, and replace snap rings and thrust washers during a rebuild. Gear work normally needs the gearbox out, so follow the service manual or use a shop.
Brands here include Comet, Colony, Covingtons, Andrews and Jims. Pick your machine in the Ride Finder at the top of the page. See Bearings, Gaskets & Seals and Gearboxes & Transmissions for the rest of a rebuild, all part of Transmission & Drivetrain.
FAQs on gearbox and transmission parts
Why does my motorcycle jump out of gear?
Worn gear dogs, weak shift components or a shifter linkage that is out of adjustment can all cause it. Diagnosis needs inspection, because the cause may be in the shifter, the gears or the clutch. Check the linkage and clutch first, then open the gearbox if the problem remains.
What is the difference between direct drive and overdrive gear sets?
In a direct drive top gear the gearbox output turns at the same speed as the engine, a ratio of 1:1. An overdrive top gear turns the output faster than the engine, so the engine runs at lower rpm at the same road speed. Check the maker's notes for fitment.
Should I replace gears in pairs?
Yes, usually. Gears that mesh wear together, so a new gear running against an old one can wear fast or be noisy. Replace mating gears as a set and check the shafts, bearings and shift forks while the gearbox is open.
What do snap rings and thrust washers do?
Snap rings hold gears and bearings in place on a shaft, and thrust washers control end play between gears. Both can wear or distort, so fit new ones during a rebuild and use the spec your service manual gives.
Is a gearbox rebuild a home job?
It depends on the machine and your experience. It usually needs the gearbox removed, special tools, and exact end-play measurements. Follow the service manual, or have a shop do the work if you are not sure.
