Chances are since it occurs every turn of the wheel that it is either a top bearing in the column, or the steering gear itself. Disconnecting the drag link is one way of isolating the steering gear from the linkage.
Once you have eliminated the steering box, jack the front end up and have an assistant (soldier B) turn the wheel and listen for a clunk, or some indication of a flat spot on a corner of the front end or in the drag link itself.
Short story: I had a squeak in the steering in my civvy Suburban, and it nearly drove me crazy. I suspected a bearing in the upper column, and then the thing started to bind occasionally which is very dangerous. I finally found a dry bearing in the lower column. I guess the moral to my story is that this is not something to ignore. I should have gotten right after my problem right away. It is a potential accident cause and needs to be diagnosed immediately. If you jack the truck's front axle up, you ought to be able to determine where the problem is before taking anything apart.
RL