Transfer case requires less than 1 litre. Uses the BMW fluid (x-drive). Manual says that adaptations need to be reset after changing it.

Differentials are about 1 litre each. I would buy three litres, in case you need the last bottle. 75w-90, not limited slip.

I would expect that the transmission fluid is ATF, but I would look for a tag on the side of the transmission case to confirm that. Different fluids have been used at different times.

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2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue