When you adjust that steering gear box, (as above, very easy to do) test drive and make sure the steering wheel returns on its own following a turn. If you tighten too much, the wheel will remain following a turn and you'll drive your truck into someone's living room!!! Putting in oil is also an easy next step. After that it gets pretty hard.
All the components of steering from the king pins to the steering gear box are probably worn such that each component puts some measure of play in the steering. It called backlash when machinery gets worn and has wiggle in it that cannot be compensated for by way of adjustment.
