check your final drive / differential aeration

[shogun]

The final drive like the automatic transmission and the engine need an air breather system, as the oil expands when hot and get's less in volume when cold. To avoid vacuum or pressure inside the systems, there are simple air breather 'valves' installed, on the trans on top at the end for example. Maybe not many know that also the final drive has a small hole at the end plate for this purpose, approx. 6mm.
When this hole is plugged with dirt and oil the pressure can get that high that the final drive gaskets blow resulting in heavy oil losses.

Here a pic where this hole is located, sometimes varies a bit depending on the end plate
Differential Deairation Photo by shogun_bucket | Photobucket (http://s71.photobucket.com/user/shogun_bucket/media/diff.jpg.html?sort=6&o=288)

Here a clogged one on an E36 Z3 final drive, can hardly be seen
http://img.tapatalk.com/d/13/10/02/2a2y8u8e.jpg
a bit cleaned
http://img.tapatalk.com/d/13/10/02/ydaqyhu6.jpg

[mattyb]

very interesting, I had not ever considered this. thanks shogun

[alex 1993 525i auto]

Thanks for the tip, I have to swap oil in my final drive so I'll check for this at the same time (it can be checked/cleaned while attached to the car right?)

Alex

[632 Regal]

I raced a chevy trans once and a bug (mud spider) clogged the vent tube on it. At the end of the track (1/4 mile) It would pop the filler tube out and dump a couple quarts of fluid from the heat. I always pay attention to vent tubes since then.