I took the truck in for the state safety inspection and one of the failure discrepancies was "play in the steering." I have a really good alignment guy so hopefully he can figure it out. Over the phone he suggested it could be a number of things including:
- someone tightened the gear box adjustment to reduce play when centered, which makes it excessively tight when it is off-center
- ball joints and tie rod ends are stiff from lack of regular driving

I'll update after I get it back from the alignment shop. FYI, the tires are only a few years old.