| Also known as | T3858 |
| Diagram | Fig. 10 — GEARBOX SHAFTS AND GEARS · ref 3 |
| Subsystem | gearbox |
| Listed in parts books | 1969 |
MAINSHAFT 3RD GEAR
Mainshaft 3rd gear for the Triumph four-speed gearbox, PN 57-3858 (formerly T3858).
This is the mainshaft third gear for the four-speed Triumph gearbox, listed in the parts books as MAINSHAFT 3RD GEAR under part number 57-3858, also known by its earlier T3858 designation. It lives on the mainshaft inside the gearbox shell, one of the pick-up gears that engage as you work through the ratios.
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Our catalog record only ties this one to a single appearance in 1969, so we don't have a wide fitment span documented here. If you're rebuilding a box, it's worth pulling the old gear and comparing tooth count and bore before ordering, since gearbox internals changed across model years and this is a wear item that's easy to get wrong if you go by memory alone.
Call the shop with your gearbox type or engine number if you're not sure this is the right gear for your box. We'd rather confirm before you order than have you sending it back.
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