i have just put in a new rear transmission seal and was inspecting the old one when i realised there was a hole in it and upon closer inspection a labeled ''up'' and ''down'' which i couldnt see in my poorly lit garage, and more annoyingly - not mentioned in the service manual either.
So my question is thus - how crucial is the orientation of this seal.

My guess is that the hole is to allow the prop shaft to slide in or out and not have the pressure deform the seal (luckily i happened to put the seal in with the hole at about 7oclock anyways so i might just roll with it)

 

That's news to me! I know I replaced mine at some point, don't know if I even noticed that. I'm sure it's there for a reason, not sure how important it is.

Dale

 

I think you will be fine, I had the same question when I did mine in my FC,

I talked to someone that builds a lot of mazda transmissions and said the small hole should face down

 

It's a moisture drain. If it's upside down it could possibly get full of water from heavy rain or a large puddle. Real world it probably won't be a problem unless you plan to do some river crossings.

 

^Thanks, that makes sense. 'Nice to know' trivia. I've probably changed mine three or four times over the years, the last just a few weeks ago. Never noticed the hole but never had issues. Still, next time I put one in, I'll put the hole at the 6.