Thanks for posting.
Switched out to Redline MTL and Redline 75W90 for the rear diff. Did the M3 trans bushings at the same time, shifts are much much better now! 60,000km and the oil is a very dark brown, glad I didn't wait another 40,000km! FWIW, used gravity feed for both... takes a long time but it works just fine with 3/8" dia PCV hose and a funnel. Just get the funnel higher than the transmission or diff and gravity does the rest. Having something to hang it on helps while you drink your beer
