A lot of things can contribute to driveline noise, bad rear end bearings,driveshaft support bearings, maybe a u-joint.Is it noisy in both high and low range? Its not unheard of for the differential bearings to fail. A roar during acceleration and coasting could be worn carrier bearings or a worn gear set.Have you pulled the inspection cover to check the gears for faults like pitted gears or the presence of metal in the lube oil? The picture in my repair manual doesn't seem to show a bolt as you describe on the 2 spd axle.The single speed axle has a thrust pad adjustment bolt similar to what you mention.For sure check the driveshaft support bearings and the driveshafts. You should be able to find a manual for your truck from one of the vendors listed on the Stovebolt links page.