Don't use Mercon V use either Ford XL-12 or Valvoline Transfer Case fluid is what I use in all my vehicles. 91 F350, 93 F150, 00 F350, 05 Explorer and an 05 F250. Dex/Merc and LV will work too I just use stuff designed for T-cases personally.
Valvoline Multi-Vehicle (TCF) Conventional Transfer...