[Fot] 1966 TR4a transmission help

[DAVE HOGYE]

Yes, do as Tony suggests.  
The set screws have been known to back out and drop into the works or, the square end breaks off and falls into the works.  This can immediately stop rotation of the works and the rear tires.
The end of the center shift rail can pull out of the rail.  I have seen this.  A tach weld will secure the end in place.
One more tip to help stop leaks.  Be aware that just about every threaded bolt hole in the case goes through the case.  Sealant should be used, or leaks will be plenty.  The 4 input shaft bearing carrier bolt holes also go through the case.  They will leak without sealant.  
The engine block is like this too.  A number of bolt holes go through the block.  They all need sealant.  Like the two coil bracket holes and the generator/alternator bracket.  I prefer to not mount the coil on the engine, so I use crush washers under the bolts there.  
Stay connected with the group during your project and good luck.
The FoT archives is also a great resource for tips.  
 
Dave H.
 
 

> On 10/22/2025 7:31 AM PDT Tony Garmey via Fot <fot at autox.team.net> wrote:
>  
>  
> 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
> > 
> > <IMG_2832.jpg>
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