| Also known as | T1558 |
| Diagram | Fig. 10 — CHAINCASE AND CHAINS · ref 1 |
| Subsystem | primary |
| Listed in parts books | 1964–1969 |
Gearbox sprocket (17 th) 3TA, T90
17 tooth gearbox sprocket for the 3TA and T90, later superseded by 57-1476.
This is the gearbox sprocket, 17 tooth, off the output shaft of the gearbox where the primary chain picks up drive and sends it back to the clutch. It sits inside the chaincase, and our records tie it to the 3TA and T90 machines. The legacy book number for this one was T1558, and you'll also see it listed as SPR-TA17T on some supplier sheets.
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Being a 17 tooth sprocket, it's a specific gearing choice, so if you're chasing a sprocket for one of these smaller unit twins, count the teeth on what's coming off before you order to make sure you're matching what's currently fitted.
Triumph superseded this part number with 57-1476 down the line, so if your parts book or an old invoice shows this number but the part you actually need shows up under 57-1476 now, that's the same physical sprocket under its later factory number.
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