I'll be changing the oil in my transfer case (95 Bronco, Borg-Warner 13-56) soon, and wonder what would be the best lubricant? Mercon, Mercon V, or some kind of concoction like 1 pint of synthetic 75W-90 and ATF. The fluid recommended by Ford is Mercon multi-purpose ATF XT-2-QDX. Would the difference between Mercon and Mercon V be significant in this case?
I prefer synthetics. I would use either Mercon V or Mobil synthetic ATF. You don't state how many miles are on the Bronco but since it's a 95 I assume it has quite a few. A transfer case isn't subjected to heat like an engine or transmission so it probably doesn't matter, Mercron or Mercon V. I would stay away from mixing with gear lube.
Probably not, but I would stick to mercon. Do not use any gear oil. Since it takes only 2 quarts, synthetic would not be real expensive change, but I am not convinced that a transfer case needs synthetic. I used Valvoline durablend in mine and 30k later it started having problems jumping out of 4wd. Probably not the oils fault. I don't think a transfer case is very hard on oil and under normal 2wd service doesn't have that many internals in motion. I would recommend staying with Mercon.
I've read somewhere that Mercon V is more slippery than plain Mercon, and while that's no good in a tranny designed for Mercon, in the case of a transfer case there are no clutches and bands where a precise amount of friction is needed for proper functioning.
A friend of mine who had a repair garage had a truck (Ford) come in with a blown transfer case. The customer had bought it used and had said before he bought it the transfer case had been rebuilt.
Well after removal my friend openned up the case, it was empty, with no sign of fluid ever being in it.
But inside he found there is a small pick up pump driven off the main shaft, which must help in keeping the chain and bearings lubed as apposed to the chain just being bathed
in the lube.
So a synthetic I think would be the best choice, I've changed it in my Bronco II and Explorer. I also put synthetic ATF in my T-Birds manual trans, and it made a big difference in the winter.
Full synthetic Mercon is your best bet. Brands like Mobil1 and Royal Purple ATF fit the bill nicely. Ford even makes a 100% synthetic Mercon (part # XT-2-QSM) which you can order. These are all top notch fluids that far exceed Ford's specs and requirements for your particular application. No need to get into the Mercon V thing.