HOME and how to join Forum Open Area General Scott topics Gearbox Studs Re: Gearbox retaining studs/bolts


Hi Maurice. Earlier handchange boxes and 1930’s footchange boxes have three eighths Cycle thread studs (26TPI), and later boxes, including Birmingham boxes, have three eighths BSF bolts, which make removal and installation of the gearbox much easier. Be VERY CAREFUL that any new bolts, when tightened up, do not protrude into the works, or you will have a major disaster on your hands!! The only drawback to bolts is that oil does tend to seep down the threads, so use PTFE tape on the threads when installing. Obviously you can use Cycle thread bolts instead of studs on the earlier boxes. Do use the correct large diameter washers to spread the clamping loads on the alloy tray, or a steel plate about 4″x1″, which is even better if you are not concerned about originality. Hope this helps. Regards. Brian Marshall.