| Also known as | T3988 |
| Diagram | Fig. 12 — GEARBOX SHAFTS AND GEARS · ref 7 |
| Subsystem | gearbox |
| Listed in parts books | 1970–1972, 1974, 1976–1980, 1983, 1985 |
| Also fits (as replacement) | 1960–1962, 1964–1965, 1967–1968 · for PT108B |
CLUTCH ROD BUSHING 650/750 TRI - Replaces PT108B
Brass-era clutch rod bushing for Triumph 650/750 unit twin gearboxes, replaces PT108B.
57-3988 is the clutch rod bushing that sits in the gearbox mainshaft on Triumph 650 and 750 unit twins, per the catalog entry. It's a small but important part: the clutch operating rod runs down through the hollow mainshaft to work the clutch, and this bushing is what that rod rides in and against as it moves. Wear here shows up as sloppy or inconsistent clutch action even when the rest of the clutch is in good shape.
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This number replaces the older PT108B designation, so if your parts book or an old drawer of spares still has that stamped on it, you're looking at the same physical part. It shows up across several gearbox figures in the catalog - shafts and gears, inner cover and selectors - which tells you this bushing gets referenced whenever those assemblies come apart.
It's a cheap part to have on hand when you're into the gearbox anyway, since checking the bushing while everything's stripped down beats pulling it all apart again later because the clutch action went vague on you.
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