I checked a few R200 vents I have. The arrow points forward. My finned R200 cover has a metal vent which remains closed until the spring loaded valve is opened to relieve the excess pressure. I measured it if you are interested in swapping one of these in place of the plastic one. It is 14mm. Don't know the part number or availability off hand.

Edit - After removing and studying one of the plastic vents from a R200 cover, I can't see any reason why the arrow couldn't also point to the rear as long as the through holes in the case are oriented to the sides, which they would be either way.

Edited January 6, 201114 yr by geezer

I measured it if you are interested in swapping one of these in place of the plastic one. It is 14mm.

Is 14mm the size of the opening in the diff cover? If so then the R180 is considerably smaller. The larger part of the vent is about 14mm but it steps down in size before going into the cover.

Hi Steve, I pulled the plastic vent assembly from a R200 cover and measured it at 14.3mm. I measured the hole in the cover that it press fits into and got 11.8mm. I did not remove the metal vent assembly from my R200 finned cover but measured the diameter of the tube that was accessible outside of the cover at 14mm. I'm sure they would be interchangable. The metal spring loaded vent assembly does not protrude through the cover but only into it and therefore does not have the smaller holes which have to be orientated in the proper direction. I didn't have a R180 on hand to compare with.

Perfect! thanks.

I wonder if a piece of sponge or cloth or maybe a plug of Scotchbrite might stop the splashing, but still let it breathe.

Last weekend, I rolled up a piece of nylon window screen, folded it in two and shoved it in the vent tube. This seems to have done the trick as I now have a bone dry diff cover.

I think the wadded up screen allows air to move in and out of the diff due to heating/cooling cycle but provides lots of surface area for a mist of gear oil to deposit. The gear oil droplets can then flow back into the diff.

Anyways, whatever the reason, the little wadded up screen seems to be keeping my rear end clean.:laugh:

Anyways, whatever the reason, the little wadded up screen seems to be keeping my rear end clean.:laugh:

No more wiping babies rear ends that would be nice:stupid:

Steve, I was out staring at an old R200 yesterday and convinced myself that some of the oil is actually leaking up past the vent/cover interface, where it presses in. If you look at the surface of the plastic where it has the interference fit with the metal, it is a molded in rough surface. Probably so that you can get it in and out easily. But the rough surface offers an easy path out for hot oil. Even though it's up hill, a little dust and dirt acts like a sponge, drawing more oil out.

I managed to crawl up under my car and remove the vent on the R200 in service in my car, throw a little silicone sealer on the sealing surface and pop it back in. I'll see how it works.

How is yours doing so far?

There is also a special R180 diff cover gasket for the front diff in 4x4 720 pickup that has a shield that covers the vent hole in the bottom of the vent tube. That stops most oil venting out the tube. I also drilled and tapped the hole int he cover, put in a brass barbed fitting, and ran a loop of tubing.

I placed mine with the arrow pointing forward. No leaks so far. R180.

I use special classic car line oil from Kroon Oil for my diff

Datsun - 240Z S30 (1969-1973) - Rear axle - Product recommendation - Kroon-Oil