Triumph Gearbox Sprocket 18T Pre-Unit PN# 57-0471 A

The gearbox, or “countershaft” sprocket is important as it connects the primary drive to the final drive. Gearbox sprockets are available in different sizes to accommodate varying needs and riding conditions.

Suitable for fitment to the four-speed Triumph pre-unit models from 1947-1962. The 18 tooth gearbox sprocket is compatible with the 5/8″ x 3/8″ pitch 530 chain. Changing to an 18t sprocket from a 19t will result in a lower gear ratio through all four gears. Sourced from Wassell in the UK.

The gearbox sprocket is fitted to the main shaft of the transmission. It transmits power from the primary drive to the rear sprocket. Must be used with a 530 chain.

The sprocket is fitted to the splines of the high-gear assembly and retained with a large nut. The clutch assembly must be removed to access the gearbox sprocket. Refer to the factory workshop manual for installation procedures.