I had to do some work on the car and while I had it lifted I checked the rear, looking for a clunk I have but still wasn't able to find it.

Unfortunately the differential was leaking so much fluid it actually had a droplet at the bottom, so not a simple weep. I'm pretty sure the source of the leak is the output shaft seals (the input seal is fine), although it could be the gasket holding the two together? That part is afaik discontinued.

Maybe the same thing happened to me that happened to Dave:
http://www.zhpmafia.com/forums/showt...since-changing

I'm seeing two different part numbers depending on the diagram:
Part 14 here:
http://bmwfans.info/parts-catalog/E4..._drive_output/
Part 8 here:
http://bmwfans.info/parts-catalog/E4...ve_gasket_set/

If I go for a rebuild or something like that, is there any "while you're in there" stuff I should consider?