[Fot] 1966 TR4a transmission help

[Tony Garmey]

The oem vent is a small hole in the tail shaft under the shift tower.
If your sure that the o rings are leaking - go ahead and pop of the gearbox top and …
*Add a dash4 fitting for a vent
*drill and lock wire the set screws that loc the selector forks to the rails
* tach weld the centre blade at the end of the rail .
* change the o rings

British frame and engine for the majority of the engine parts.



Sent from my iPhone

On Oct 22, 2025, at 7:23 AM, mhmolson--- via Fot <fot at autox.team.net> wrote:


Good morning, I have an issue with transmission oil leaking out of the three o ring seals where the transmission selector shafts enter the top cover. This only happens during high rpms. This is an overdrive unit.
Has anyone added additional venting to the top cover. I understand there is possibly a small vent hole in the front however I have not looked at this yet. I am also going to build a TR4 motor this winter and am looking for direction and contacts for pistons, liners, and rods. I am good at mechanical logistics, and I have built two strokes, I have also been around engine builders and understand, however this will be my first real build. Yes, I understand that certain things will be left to the pro’s
Help appreciated
Matt
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