Index to Hermit's 650 Triumph Gearbox Articles

These articles pertain to a 1969 Triumph T120R 650, as well as other late-60s 4-speed gearboxes using a plunger and spring. If you're researching a 5-speed gearbox, or a gearbox using a leaf-spring instead of the plunger, be aware that there are important differences. See links at the bottom of this page.

Disclaimer: I am not a gearbox guru. However, I have collected a lot of info,
and a lot of photos and illustrations about Triumph unit 650 gearboxes, as well as links to
many valuable resources, and placed it all at your fingertips right here.

Links to the Articles


The Bonnie Ref: A Hyperlink Junkie's Field Guide to the Bonnie: Gearbox

This is the Gearbox chapter of Hermit's "The Bonnie Ref". It's loaded with info on tearing down, inspecting, and reassembling the gearbox parts, complete with descriptions, diagrams, specs and more, with links to pertinent factory bulletins, forum discussions, and other sources.

Triumph 650 Gearbox in Photos & Photo Animation
Front View
These photos show you exactly how the camplate and gears move in all the gears, either in stills or as a unique animation of the Triumph 650 gearbox.
Triumph 650 Gearbox in Photos & Photo Animation
Rear View
The same great gearbox photos and photo animation but viewed from the rear.
Triumph 650 Gearbox Reference Photos
Clear, detailed photos of all the gearbox parts, including the mainshaft, all the gears, the camplate, and plungers. For several parts, old and new examples are shown, illustrating wear and upgrades.
Triumph Gearbox Assembly Methods Comparison
There are many ways to put a Triumph 650 gearbox back together. Here's a side-by-side comparison of the methods described by the Triumph workshop manual, the Haynes workshop manual, and, the master himself, Hughie Hancox:
Hancox Gearbox Assembly Method
Here's a step-by-step description with photo illustrations of the clever way Hughie Hancox stuffs a Triumph unit 650 gearbox. It just can't get any easier than this! I'm laughing the whole time I'm doing it this way - how can it be so easy!
Camplate & Quadrant Indexing
Having trouble indexing your Triumph unit 650 gearbox's camplate and quadrant? These photos and descriptions will make indexing a snap, whether it be in first gear, fourth gear, or neutral between 2nd & 3rd. Shows you exactly how to position the camplate and the quadrant for whatever method you use.

Links to 5-Speed & Leaf-Spring Gearbox Info

  • From, John Healy on Indexing Triumph Gearboxes threads on indexing Triumph gearboxes. These threads feature posts by John Healy (Triumph Board moderator), and he references the differences between 4- and 5-speed gearboxes as well as gearboxes using spring and plunger versus those using the leaf-spring.
  • From, Kevin Robert's post on upgrading a 5-speed gearbox
    Kevin's post is profusely illustrated with photos and should be a great help if you're delving into a 5-speed.