WHAT? They are not "finicky" on the fluid used, just like any TC follow spec and you will be fine. People try to make these units out to be something mysterious and strange when they are actually simpler than the part time units are. The quickest and most positive way to tell if your VC is going out is just put the case in 4 low and drive it a few dozen feet and immediately return it back to 4 high. The VC will have spooled up, and when taken out of gear will get extremely loud as you try to put case into high range, even with the transmission in neutral. This will show up before the front end starts "chirping" when turning. Another point to remember is it is imperative to EXERCISE the vc regularly. Simply put the TC in low range and drive it around the block once or twice. The fluid in the coupler is so thick it is almost a paste. Doing this keeps all the plates wetted with it, as well as ensuring the fork's internal workings are lubricated, thus ensuring Minimal wear. One of my grand Cherokees has well over 250K on the original VC with no issues yet, because it is regularly used, keeping the plates wetted so that they don't wear. The fluid in the case is replaced at the specified intervals which keeps internal heat transfer optimal and prevents the fluid in the VC from breaking down as well. Like I said there is no big secret on the fluid the cases use. Any factory speced will work fine. Just do the called for maintenance and you will be fine.
As I stated originally this is most likely an issue with the CV joints at the front wheels, these get the most wear and tear when being flat towed, Doesn't matter if its a 4wd or a front wheel drive, this is an extremely common issue And is why the more experienced motor home owners forgo tow bars for tow dollies. The Dolly has it's own wheels which removes the towed vehicles steering and front drive components completely from the equation, it also prevents the towed vehicles odometer from spooling up the miles when towed.