With the wheel jacked up, grab the tire top and bottom with the grease cap removed, and look for play between the hub and the spindle. That would be bearing wear and/or preload adjustment problems. If the whole spindle moves, you have kingpin and/or bushing wear problems. With the steering wheel locked in the straight ahead position (I use a bungee cord to the seat frame) try to shake the wheels by grabbing the front and rear of the tires. Look for looseness in the tie rod ends, drag link (between the left front spindle and the steering gear, and/or movement of the Pitman arm that comes out of the side of the steering gear and hangs down next to the frame. Sometimes slack can be fixed by tightening adjustments, otherwise you'll need to rebuild or replace the worn steering parts. There can also be looseness in spring shackles, spring pivots, and other suspension parts not directly involved in the steering system. Once you find the source of the looseness, post a new thread in the "Driveline" forum. You'll get plenty of help there to make your truck safe to steer and stop. That's always the first concern to address, before making it go faster.
Jerry
