Hey
OB,
OK - diffs are easy (well, the front less so because of the reinforcement plate). Something like Redline 75W90 or Castrol Syntrax Long Life 75W-90 - three litres need (quarts over there?), as the rear takes about 1.4l and the front takes about 0.7l (typical...). Levels are checked by filling to fill port...
Front will be black and nasty - rear should be clean. I think the engine heat toasts the front diff...
TIS front -
https://www.newtis.info/tisv2/a/en/e...eneral/EVdex6b
TIS Rear -
https://www.newtis.info/tisv2/a/en/e...-drive/DyNXa4H
I've never replaced and sealing rings/gaskets but they are cheap enough...
Similar process for ATC500 transfer case, use BMW DTF 1. The fill plug is hard to get to - good luck torqueing it down - I just did it up tight (could only get a ring spanner in there).
Reset of the oil wear adaptations - I've only used DIS (v44) but I understand you can also use ISTA-D and I think the Foxwell unit will do it too (among others). You CANNOT use INPA or PA-Soft.