| Also known as | T4055 |
| Diagram | Fig. 9 — GEARBOX INNER COVER AND SELECTORS · ref 17 |
| Subsystem | gearbox |
| Listed in parts books | 1970–1972 |
CAM PLATE TRIUMPH 650 4 SPEED GEARBOX - Replaces 57-3650 57-0500 - May required changing plunger spring - some years
Cam plate for the Triumph 650 four-speed gearbox, part of the selector mechanism inside the inner cover.
The cam plate is part of the selector mechanism inside the gearbox inner cover, the piece that translates movement from the selector fork shaft into the specific gear engagement pattern of the four-speed box. As the gear lever moves, the cam plate rotates through its indexed positions to hold each gear selected until you shift again.
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57-4055 (also T4055) is the plate for the leaf-spring-indexed 650 four-speed box of the early 1970s. It is not interchangeable with 57-0500, which is the narrower plate for plunger-indexed gearboxes; each type of box needs its own plate. The catalog notes that fitting this cam plate may call for a different plunger spring on some years, so check which indexing your box uses before you order.
If you're rebuilding a box from that era, it's worth having the old cam plate on the bench next to the new one to compare the indexed profile before you commit to the swap.
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