You probably need to crawl underneath and do a little diagnosis. I would guess that the most likely culprit is a worn track bar. If the ball joint on the one end of it moves more than 1/8" when the wheel is turned back and forth a bit with the engine going, it's worn out.
What works for me is a combination of a new track bar (got it from NAPA, with lifetime warranty), and a DSS (Darin's Steering Stabilizer). Takes less than 1/2 hour to replace track bar, and not much more than that to install the DSS, which won't need replacing. Truck steers much better than new.
Darin's new track bar mounting bracket and a third-gen track bar is supposed to be a better fix for the pooorly-designed 2nd gen track bar.