[Kracka]

Switching from a synthetic to a conventional poses no problem at all, do it at your will. Rotella-T is a very good oil, 15W-40 works great in the summer and the 10W-30 in the winter (or 10W-30 year-round).

As for tranny/diff fluids, use a mix of 2 quarts of Redline MT-90 and 1 quart MTL for the transmission; for the rear differential use Mobil 1 or Redline 75W-90.