There are a few things you can do to diagnose your slop. You will need a friend, a jack, and a flat spot to jack the truck up on.
Put your friend in the driver seat, with the truck running. Crawl under the front and have him slowly move the steering wheel back and forth to take up the slop. You should be able to identify what's not moving with the wheel.
Second. Jack up the front of the truck a little ways. And sit straddling the wheel. Grab the wheel at the 12:00 and 6:00 position and try to jiggle it. If no movement, you are good. If more than a hint of movement, you likely have wheel bearings going out. Next grab the wheel at 3:00 and 9:00 and again jiggle the wheel. If you get more than a hint of movement, you have inner or outer tie rods going out. Your buddy should be able to see witch ones are moving while you jiggle the wheel.
Move the jack to under the control arm or under the ball joint, again jiggle the wheel from the 12 and 6 position. And see if it jiggles. If you get jiggling, either have you buddy look and see where the movement is, or have him jiggle it while you look. If you have jiggling that is not the wheel bearing, it's the upper or lower ball joint or both. In order to find out, the weight needs to be off the ball joints. That's why for them you put the jack under the ball joint or under the control arm.
The screw on the top of the gear box the others are telling you to adjust to pull slop out is only designed to be turned very little. Think in the 1/8-1/16 of a turn.
Hope that helps.
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