| Diagram | Fig. 6 — Gearbox: Shell, Gear Cluster, Sprocket, Mounting Bolt · ref 15 |
| Subsystem | gearbox |
| Listed in parts books | 1975 |
Norton Gear, 2nd. Mainshaft
Norton gearbox mainshaft 2nd gear, part number 06-4640.
This is the 2nd gear from the mainshaft cluster in the gearbox, part number 06-4640. It's a Norton part, not a Triumph one, despite what a heuristic tag might suggest — the description and catalog listings both point to Norton gearbox use.
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This gear lives inside the gearbox shell as part of the mainshaft cluster, working alongside the other mainshaft and layshaft gears to give you second gear when you're shifted into it. Wear on these teeth or the selector dogs is usually what brings a gearbox in for a rebuild, so if you're replacing this one it's worth having a look at the rest of the cluster while it's apart.
Our catalog record only shows this part turning up once, tied to 1975, so we don't have a lot of cross-year history to lean on. If you're not sure this is the right gear for your box, give us a call and we'll sort out fitment before you order.
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