I have a 1925 Model P Triumph which was jumping out of second gear.
This video shows the gearbox components and follows the process of rebuilding and setting the gears. The common faults are ;
- incorrect setting of detents in gearbox causing misalignment of travelling gear.
- incorrect setting of gear lever against gearbox causing the mechanism to "hunt" for position
- wear on dog mating faces allowing transmission forces to disengage gear.
