135i auto diff cooling


New Member
Jul 30, 2018
New to the forums, having done some research on lsd diffs and autos I am having a hard time finding cooling options on a small frame auto diff.
Firstly, I’ve been reading of individuals “cooking” their lsd diff fluid under track use. This appears to be attributed to the lack of passive or active cooling offered to the small stock pumpkin. To combat that issue the most popular option I’ve seen is the passively cooled billet V.A.C. diff cover. Problem being the auto while having an ideal final drive ratio (3.46) are of the “small” variety and don’t fit the V.A.C. cover. The V.A.C. cover is nice in that it has drain port that the OEM lacks for active cooling if you wanted to do so.

To cut a long story short, what options does an owner of an auto diff looking to upgrade to a LSD have has far as cooling without doing a manuals 3.08 lsd swap? (Yes I know for aprox 9 mo there was a large 3.46 offering) Is the logical thing to do just buy a good condition, large, manual 3.08 diff and swap in the desired L.S.D. and get the appropriate shafts to match? At which point I could go ahead and buy a V.A.C. cover and/or diff cooler+pump ect?



Oct 18, 2016