| Diagram | Fig. 12 — GEARBOX SHAFTS AND GEARS · ref 22 |
| Subsystem | gearbox |
| Listed in parts books | 1974, 1976–1980, 1983 |
GEARBOX SPROCKET 20T - 5 SPEED TRIUMPH 72-ON - UK
20-tooth gearbox output sprocket for 5-speed Triumph twins, 1972-on.
This is the 20-tooth gearbox sprocket for the 5-speed Triumph twins, catalog listed for the 1972-on range. It mounts on the gearbox output shaft and carries the final drive chain back to the rear wheel sprocket, so it's a wear part worth checking whenever you're in there for a clutch job or chain and sprocket set.
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The catalog lists this under 57-4782, also cross-referenced as SPR-5SP20 in some listings. It shows up in the gearbox shafts and gears section of the parts book, which is where you'd expect to find it alongside the mainshaft and the gear cluster it drives off of.
If you're rebuilding a 5-speed box or just replacing a worn sprocket, pull the old one and compare tooth count and spline before ordering — the catalog record ties this to the 1974-1983 span, but confirm against your own gearbox before assuming fitment.
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