Is the manual transmission vent on the FD serviceable or replaceable? Preferably while still on the car? I recently replaced my output shaft seal after i noticed a leak and when i opened the fill hole on the trans a bunch of pressure came out like a champagne bottle pop, I figured it may have been previously over filled, Now after fixing the seal and changing new fluid to the proper level i still seem to have a leak. I took the metal cap off the top of the vent everything looks clean but i can't tell if it's operating correctly, is it spring loaded for a certain pressure relief? Is there a part number for this vent?

 

There won't be a part number, it's part of the case and would be a challenge to remove on top of the box in situ. Haven't removed the gearbox vent, but the diff one comes out and would be identical process - light press fit.

Don't think the cap is supposed to be detachable. The way I did it, a small copper hammer, used gingerly, and switching an aluminium support to and fro on the opposite side of the tube.

 

The '93 Mazda RX7 parts catalog does show a p/n for the transmission vent (Breather Air - Mazda (M501-17-530A)).

 

Thanks for the part number, local Mazda store parts guy couldn't find anything. I might order one if available just to see how it works. Does anyone know if these are hollow tubes or is there something in there to make it a open/shut? Trying to figure out what would be causing pressure build up in my trans.

 

From looking at mine (trans is out) it looks like nothing more than effectively a tube with a slightly larger tube over the end of it. It acts as a shroud to keep anything from going into the tube and has enough play on its fitment to allow pressure to escape from 2 holes in the bottom of the larger tube. I suppose there may be something more complex than that within it, but for the price of the part (<$5) I doubt it, and it would seem unnecessary to be more complex than that.

FWIW, mine does feel a little... 'crusty' as I wiggle the top part. I suppose it would be possible to you could get enough just general detritus build-up over time that perhaps the vents, which are really just two ~1mm holes, do get clogged up. Especially if you lived on, like, a gravel road that kicked up a lot of dust under the car. I can imagine enough dust getting onto the upper part of the transmission that clogging those could be possible. Not easily, and I would think any natural pressure build-up would likely periodically "self-clean' the vents. But I could see it being possible.