Tech: Replacing A Triumph 5-Speed High Gear & Roller Bearing
Triumph 5-Speed High Gear & Bearing
Triumph 5-Speed late high gear bearing with the correct roller bearing as fitted to models from 1973-1983.
If your Triumph 5-Speed transmission is in need of a new high gear, and / or roller bearing, we highly recommend reading this post as it could save you a lot of time, money, and headaches. In 1971 for the first year, we saw Triumph 650 twins, Triumph Tridents, and BSA Rocket III's (A75) offered in an option with a 5-speed gearbox. You can identify a 5-Speed gearbox by the engine serial number having a "V" stamped after the model number. For example, a Triumph T120 "V" or A75 "V" would be a production 5-Speed model. "V" stands for 5. The early 5-Speed gearboxes from 1971-1972 are very unique compared to the later variety as used on Triumph 750 twins & triples from 1973 & on. Many often called the 1971-1972 gearboxes "weak" and prone to issues. Although that is somewhat true in one respect, I will not be getting into detail regarding that.
Parts diagram out of a Triumph 5-Speed parts book. Shows the 5-Speed gearbox assembly along with the high gear and bearing.
The Triumph & BSA 5-Speed high gear and bearing from 1971-1983 do look very similar, in fact, there are many folks that are not aware of the differences. These differences are crucial in how your transmission will perform. Early 1971-1972 5-Speed gearboxes used a different high gear and bearing compared to the 1973 & on models which include the Triumph T140, Triumph TR7, T160, and others. 1971-1972 5-Speed gearboxes I will refer to them as "early", and the 1973 & on types I will refer to them as "late". The early 5-Speed high gear and bearing are very hard to find and were always sold together because they should only be used together. Above, you will see an image taken from a Triumph parts book. You can see the red arrows indicating the 2 parts, the high gear and the high gear bearing. Notice how each part has a number next to them except the parts pointed out by the arrow? That's because the high gear and bearing was sold as an assembly. Early high gears have a much wider race surface for the roller bearing. That is the key reason why you cannot "swap" later bearings and early gears together. If done, your gearbox could fail and perhaps seize.
The 5-Speed high gear acts as an inner race for the high gear roller bearing. The high gear race is prone to wear due to this design. Threads have been heat treated to ensure longevity.
With early 5-Speed gearboxes somewhat rare, most have been replaced over the years to the later types. The new 5-Speed high gear and bearing we stock is suited for the later Triumph 5-Speed models but can work on the early gearboxes. For a very long time, the high gear bearing was almost impossible to find. The high gear we stock is under 57-4780 and the roller bearing is stocked under 60-4100. The roller bearing was originally made by RHP and is now made in Taiwan, I have found that the early 5-Speed gearboxes used a Hoffmann roller bearing, similar but different. In short, if you use the 57-4780 high gear and the 60-4100 in conjunction, I repeat, in conjunction, it will work and fit on all Triumph & BSA models that used the 5-Speed gearbox from 1971-1983. You might ask, why do we sell them separately if they must be used together? We offer them separately because the 60-4100 roller bearing was fitted on models from 1973-1983, it's only for those that have the early 5-Speed gearbox that need to use them together.
Just to be clear, the 57-4780 gear and 60-4100 bearing was standard equipment on late Triumph 5-Speed models from 1973-1983. If you have an early 1971-1972 5-Speed and your bearing or high gear needs replacing, you must use 57-4780 and 60-4100 together to work. 60-4100 roller bearing is manufactured again by L.F. Harris along with the high gear itself, they are both a very high quality part designed to exceed original specifications.
Part Type Triumph Part # Country Of Origin Material
5-Speed High Gear 57-4780 Taiwan Treated Steel
Roller Bearing 60-4100 Taiwan Steel Rollers & Brass Cage
I have a ’72 T120RV; can I fit a complete T140 5 speed cluster?