Originally Posted by
Mick_Marsh
It's not a theory, it's a stated fact.
I've been there as have many others. You can learn from our experience or confirm our findings.
The LT95 transfer case gears are shimmed on the shaft. The thicker oils don't get into the oil grooves of the shims, the shims get hot and burn, melt.
The common fix up is to run a tapered bearing kit through the transfer case. Your friends ex military would more than likely have the tapered bearing kit in it. It may be able to handle gear oil but, will you risk it? Would he risk it?
Let us know what you decide and how you go.