Adjusting the pinion angle should not be done with just a 2" lift. Since your control arms are stock so the pinion angle hasn't been raised, odds are good you just need to drop the t-case skidplate by about 5/8" by stacking enough washers around all six t-case skidplate mounting bolts, placed between the frame and skidplate. Due to the indentation the washers sit in, you will need more like 3/4" to 7/8" worth of washers to lower the skidplate 5/8? Just use heavy duty galvanized washers with a 1/2" bolt hole through them. Support the skidplate with a jack, loosen all 6 bolts but only remove all the bolts on one side at a time to insert the washers. That will keep the skidplate in alignment instead of slipping off to the side if all six bolts were removed at once. Dropping the skidplate 5/8" will reduce the excessive angle the rear driveshaft u-bolts are operating in that causes the vibrations.