| Also known as | 57-0916, T3857 |
| Diagram | Fig. 10 — GEARBOX SHAFTS AND GEARS · ref 2 |
| Subsystem | gearbox |
| Listed in parts books | 1960–1962, 1964–1965, 1967–1970 |
Mainshaft 2nd gear (20T)
Mainshaft 2nd gear, 20-tooth, for the gearbox cluster, part 57-3857 (aka T3857, 57-0916).
This is the mainshaft 2nd gear, a 20-tooth gear that lives inside the gearbox on the mainshaft, part of the gear cluster that gets picked up by the selectors when you shift. It shows up in the parts book under GEARBOX SHAFTS AND GEARS, and the catalog record ties it to appearances from 1969 into 1970. If your parts book still uses the old T-prefix system, this one was listed as T3857, and it's also carried under 57-0916.
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As a mainshaft gear, it works opposite a matching gear on the layshaft, and wear here usually shows up as noise or trouble holding a gear rather than a dramatic failure. If you're rebuilding a box and pulling the cluster apart, it's worth eyeballing the dogs and the bore for wear at the same time.
We don't have more detail on this one beyond the figure and the years it's listed under, so if you're matching it against a specific gearbox, give us a call and we'll confirm fitment before you order.
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