Hey everyone, here's a quick tutorial on how to change the differential fluid on a BMW 1M Coupé.
This tutorial works also for the BMW E9X M3 as the differential is the same.
Link to part number:
http://bmwfans.info/parts-catalog/83222282583
SAF-XJ 75W-140 + FM booster
As a tip, I would suggest to raise the car slightly on the passenger side while filling the diff to allow a slight overfill, then lowering the car to make it level again and let the oil in excess to drip out... like this you know it is properly filled.
WARNING: Do not use any other oil than the bmw-recommended otherwise grinding noise during slow cornering might happen.
See Service Bulletin 33 01 02 (850)
DISCLAIMER: I am not responsible for any damage or injury that might occur if you follow this instructions. I am not a professional mechanic, just a regular enthusiast.