Originally Posted by Dr. Flyview
So I purchased a used 3.23 M3 limited slip differential (LSD), put it in the car with some friends. Noticed a small leak. We figured we needed to replace the fill and drain plug washers, so we did, but the leak remains.
Then we figured it might have been overfilled and leaking from the vent. We checked if it was overfilled, and it WAS. However, even after letting it drip out from the fill plug on a level hoist, it continues to leak. Probably about a drop every hour. It SEEMS to be coming from the bottom of the rear diff cover and continues to leak even after the car hasn't been driven for a week. This, to me, means it can't be leaking from the vent, which is higher than the resting level of the fluid? What about the output shaft seals?
1) How likely is it to be coming from the cover?
2) Is there a gasket there? What do I seal it back up with after opening and cleaning?
3) What torque should the cover bolts be torqued to?
Unless you see a path from where the oil is coming from; I would most likely suspect it is the cover. Since it is a drip- almost equivalent to a sweat. Drain it and remove and replace the gasket in between and as Rich said make sure it is dry and oil/grease free or you will run into it again regardless of what gasket material you use. When the front seal leaks it usually runs towards the back of the diff while driving. I had diff's that sweat and always left residue on the casing but never drip. I'd think since gravity is amazing it most likely is coming from the lowest point- the cover.