| Also known as | S681 |
| Diagram | Fig. 12 — CLUTCH AND CLUTCH OPERATING MECHANISM · ref 32 |
| Subsystem | gearbox |
| Listed in parts books | 1969–1974 |
Nut – clutch hub to mainshaft (9/16 UN.F)
Nut that secures the clutch hub to the gearbox mainshaft, 9/16 UN.F thread, also listed as S681.
This is the nut that secures the clutch hub onto the gearbox mainshaft, listed in the parts books as 9/16 UN.F thread. It shows up across the clutch and clutch operating mechanism figures, the clutch shock absorber figure, and the gearbox shafts and gears figure, which tells you it sits right at the heart of where the clutch assembly locates on the end of the mainshaft.
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Older parts books list this one under the S681 number, so if you are working from an early catalog and see that reference, it is the same nut as 21-0681. Catalog appearances run from 1969 to 1974, which lines up with the unit-construction gearbox era.
When you pull a clutch hub off the mainshaft, this nut is one you want in good shape going back on. If the threads or the face are worn, it is worth replacing rather than reusing a tired one, since it is what keeps the whole clutch hub assembly clamped up tight on the shaft.
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