Do a search , it has been mentioned so many times.
It appears that the silicone based fluid can not be replaced, if so it has to be around 80 something percent, the thin plates have microscopic burrs all over them.
At present we do not know of any way to service the VCU.
Ianh1 from Aussieland had some ideas about doing away with it, as did Mad Hat Man and Co., search for 2wd/4wd and Mondo mode.