When first started, the truck made a very loud and disturbing knocking sound. Turns out to have been loose torque converter bolts. Tightened them up real good, and silence followed.

The next step is to pull the bolts out, one at a time, clean the holes out real well, and instill new ARP bolts with thread locking compound to make sure this never happens again. The engine likes to vibrate things loose, as I have found...