| Also known as | T1837 |
| Diagram | Fig. 7 — GEARBOX SHAFTS, BEARINGS AND INNER COVER · ref 13 |
| Subsystem | gearbox |
| Listed in parts books | 1966–1969 |
Mainshaft 2nd gear (20T)
Mainshaft 2nd gear (20T) for the gearbox, later superseded by 57-4031.
57-1837 is the mainshaft 2nd gear, a 20-tooth gear that rides on the gearbox mainshaft inside the inner cover assembly. It's one of the gear pairs that make up the ratio set in the box, and it shows up in the parts books under the GEARBOX SHAFTS, BEARINGS AND INNER COVER figure alongside the rest of the shaft and bearing hardware for that end of the gearbox.
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Older parts books may list this one under its original T1837 form, so if you're working from an early manual and find that number, it's the same physical gear as 57-1837. The catalog record for this one runs across appearances from 1966 to 1969.
Triumph later renumbered this gear to 57-4031, so if your parts book or an older gearbox turns up that number instead, it's the same gear under its later factory designation. Worth checking your gearbox internals against both numbers if you're sourcing a replacement, since either one can turn up depending on which parts book or era your box came from.
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