Gen 2's did not have a limited-slip available, they have traction control instead, so you do not need friction modifier.
I change the rear axle every 30k myself with Mobil 1 75w-140 and take it to the Valvoline Quicky-Lube every 50k for the front (twice so far). Really the best way to do the front is to take it to the Quicky-Lube and have them do it with their suction machine. The rear axle in Gen 2's has a drain plug so that makes it easy. Get a suction gun to fill the rear and transfer case. Put down a sheet of cardboard first because YOU WILL spill some, also filling the rear is easier if you take the spare tire out and you can stick the tube from the suction gun through a hole in the crossmember. The front has no drain plug and the suction gun does not pull enough pressure to drain it through the fill plug. I know this.
The manual calls for Ford Transfer Case Lube but I've owned another Trac and several Rangers previously with the same transfer case and they all called for plain Mercon ATF. I have always used Mobil 1 ATF in them, including my '08, with no issues. At the moment I have Redline D4 ATF in it since we had some left over from changing the manual tranny lube in my son's Mustang and it is also spec'd for using in transfer cases. I have an owner project posted here on how to change the transfer case lube.
