| Also known as | T4647 |
| Diagram | Fig. 11 — GEARBOX SHAFTS AND GEARS · ref 15 |
| Subsystem | gearbox |
| Listed in parts books | 1973–1974, 1976–1980, 1983, 1985 |
Layshaft 3rd gear
Layshaft third gear for the Triumph gearbox internals, PN 57-4647 (formerly T4647).
57-4647 is the layshaft third gear out of the gearbox internals, listed in the catalog under the older T4647 number as well. It rides on the layshaft (sometimes called the countershaft) inside the transmission, meshing with its mating gear on the mainshaft to give you third gear when the box is shifted into that ratio.
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This one shows up in the gearbox shafts and gears figures across catalog listings running from 1973 to 1985, so it's a part that stuck around through a good stretch of production without a number change. If you're rebuilding a gearbox and pulling the shaft cluster apart, this is the piece to check for worn dogs or chipped teeth before you put it back together.
Since the catalog spans a wide range of years, confirm the tooth count and shaft fit against what's actually in your gearbox before ordering — gearbox internals can vary enough between setups that a part number match is worth double-checking against the physical part.
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