OP - have you seen this thread over on the 1addicts forum...
DIY: manual transmission and diff fluid change
The last few posts are mine. For my 2010 135i 6MT car BMW says to use MTF-LT-3
, but my German dealership tells me that the MTF-LT-3 has been replaced by MTF-LT-4.
On some cars there is a tag on the trans telling you which fluid it was filled with. As far as I understand it... LT-2 > LT-3 > LT4
One of the most important things is to make sure the car is level when you change the fluid. For the rear diff, I have a suction tool for evacuating fluids from Griots.