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You can run 80-90 regular gear oil in the rear differential, but if you tow heavy Ford recommends the 75-140 synthetic, or equivalent.
The transmission and t-case take plain old transmission fluid, like DexronIII/Mercon. No need to run Mercon V.
The front differential will be perfectly happy with regular 80-90 gear oil.
If your rear differential is limited slip you'll probably need to add some friction modifier. Start with just the oil and turn tight figure-8 circles and see if you get some chatter. If you do, add 1/4 bottle of the additive at a time and drive it a few miles, then repeat the tight figure-8 circles. Once the chatter goes away completely you're all set and don't need any more additive, unless you want a tighter diff, then go easy on the additive but keep in mind the clutches will wear faster without it.
Hope this helps,