Start with the easy stuff. Check the wheel bearings. Are they adjusted, greased, and snug?. Then jack up one side so the tire is off the ground. Place your hands at 3 and 9 just like a clock. Try to move the wheel. Watch from under the truck with a helper and you can see if it is the drag link or the tie rod end. Still good? Put hands at 12 and 6 try to move the wheel. This will show the king Pins. Still good? Look at the spring shackles. Are they nice and straight? are they clean and tight? Look at both the front and back on each side. Put the truck down and have some one inside to turn the wheel. Won't take much. Watch all of the tie rod ends, the drag link, and the pitman arm. If the pitman arm moves in and out of the steering box you need to set the end play or rebuild it. If the wheel moves but nothing else does then set the column end play or rebuild the box. I would bet you find something loose by the time you get to this point. Don;t forget to look at the "U" bolts that hold the axle to the springs. They should be nice and tight and not broken. While you are looking see if there is any signs of movement where the axle sits on the spring. If all of that is good get it to an alignment shop and see if something is out or bent. Castor will bring the wheels to straight after a turn. Camber will keep the wheel true to the road under load. Toe in will keep the wheels parallel in a turn. That is what those angles and measurements are all about. Good luck and see what you can find.
