Differential Vent ??

[captahab]

Im doing a differential swap next weekend on my 86lx. Ive noticed on the
rear that I will be putting in on the top of the differential there is a vent hole.
It was covered with a rubber yellow cap. I looked into the hole and you can see the axle.
I realize this is a air vent so the rear doesnt build up pressure and probably blow seals. I didnt check the rear that is coming out of my car as of yet but, is this hole just supposed to be blocked with a rubber cap ? I would of thought there would be some type of cap that would let air out but not dirt and water in. With the current set up the rubber cap fits over the hole and doesnt seem like it would let any air out at all.

Thanks.......

 

[Mustang5L5]

There is a metal fitting that screws into the axle and has a metal cap. It is vented, but designed in such a way to not easily let water or dirt in.

It's metal, not plastic.

 

[HISSIN50]

As of a couple of years ago, you could still get them at dealerships.