There have been several iterations of the Triumph 5-Speed transmission.

Not all 5-Speeds gear sets are the same. The early gear sets first offered in the 1971 model year turned out to be problematic. If used hard they would break. This wasn’t discovered during testing, but only after the bikes were in the field. When used hard, like when doing wheelies or drag starts, they would fail often breaking the crankcase in the process.

After a long wait for spare parts to repair all of the broken motorcycles sitting in dealer workshops, Triumph supplied an updated gear set under their part number CP-1000. The kit consisted of:

  1. 57-4661 Layshaft Dog
  2. 57-4654 Layshaft First Gear
  3. 57-4660 Layshaft Shift Fork
  4. 57-4653 Mainshaft First-Second Gear
  5. 57-4657 Layshaft Second Gear
  6. 57-4647 Layshaft Third Gear

There are still some early 5-Speed gear sets in 1971-1972 bikes that were never used hard and that are being used today. Just be aware that they still could cause problems. The gears included in the CP-1000 kit were finally incorporated in the 1973 model year production.