I suppose one could break down and buy from Flying Spares or Scaderia the expensive mysterious transfer case fluid and diff fluid. Would be nice to know a cross reference to this mysterious fluid. At one point I knew the specification but could not find the oil/fluid type , well maybe the dealer.


Surely most of us never thought about the differential and transfer case service. Some of this service isn't for the light-hearted. Attached is an example, front differential.

 

Maybe this Phaeton thread can help:

https://forums.vwvortex.com/showthread.php?8265673-Diff-Oil