| Also known as | T1917 |
| Diagram | Fig. 8 — GEARBOX SHAFTS AND GEARS · ref 21 |
| Subsystem | gearbox |
| Listed in parts books | 1964–1965, 1967–1968, 1970–1972 |
GEARBOX SPROCKET 18T - 4 SPEED TRIUMPH 64-72 - UK
18-tooth gearbox sprocket for the Triumph four-speed unit transmission, part number 57-1917.
57-1917 is the gearbox sprocket, 18 tooth, off the four-speed transmission. It's also known as T1917 under the old letter-prefix numbering, same physical part. This is the sprocket that sits on the end of the gearbox mainshaft and carries the final drive chain back to the rear wheel, so it's the piece that sets your overall gearing along with whatever's on the engine and rear wheel ends.
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It shows up in the GEARBOX SHAFTS AND GEARS section of the parts book, and our catalog records span 1964 through 1972 for the four-speed unit gearbox. If you're chasing a gearing change or replacing a worn sprocket with hooked teeth, this is the part number to work from.
We also stock this in other tooth counts if 18T isn't what your bike calls for or what you're trying to achieve gearing-wise, so check before you order to make sure 18T is the count you actually need.
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