Without hearing it, hard to tell what's going on in there, but since you said you just drove from Idaho ? Iowa ? (one of those "I..." states) to Cali, something you oughta check is the tranny fluid.

These things have a habit of pushing the oil from the tranny into the transfer case after extended highway use. It doesn't drain back either, leaving your tranny low on oil, and the t-case overfull. The reasons for this seem to be the seals on the shaft between the two, and probably compounded by the fact that there is no "breather" on the tranny. A common symptom is oil on the bottom of the truck that has spewed out the breather on the transfer case.

So, it's worth a check on the oil levels under there.

BTW, no, it's not a borg-warner, it's an Isuzu manufactured MUA5.