Joe, the large nut and lock ring at the bottom sets the bearing preload of the steering shaft (what the steering wheel is hooked to). You shouldn't be able to pull up on the wheel and get any movement. Tighten it as you would any wheel bearing, go tight and back off, then tight and back off, till you get a feel for where the lash ( play ) ends. You want it just tight enough the bearings make contact with the race.
The next adjustment moves the steering sector ( pitman shaft ) in and out to mesh with the worm gear ( steering shaft ). The more you move it in, the tighter the mesh is and the tighter the steering is. GM designed the gears to be extra tight right on center to hold the wheel straight ahead. This is where the scale comes into play. As you pull the steering wheel across center, it should be much tighter on one spot. Sometimes if the gear is is really worn, you can not find the center and parts will need changed. Once you find center and get the scale to read the right pounds of pull, tighten the lock nuts and you are done. Be sure the box has lube in it before adjusting.
Next thing would be to check toe-in adjustment. While the wheels are up, scribe a line around the center of the tread. Lower the truck and roll it back 4 to 5 feet then forward 4 to 5 feet so the tires and steering are setting in the normal driving position and all the slack is taken out. Take a tape measure and measure scribe line to scribe line at the rear of the tires 10" up from the ground, then the same at the front of the tires 10" up from the ground. The front measurement should be 1/8" less the the rear, or toe-in.
If you steering arms or drag link is wrong or bent, and the steering wheel is not centered when driving, you won't get a good feel in the steering wheel because of the tight center adjustment. Find out why the wheel is not centered, don't just move the wheel on the shaft. I like to check this with the drag link unhooked. Rotate the steering wheel to the far right, then count turns to the far left. Go 1/2 the distance, and the steering wheel should be dead straight. Do it a few times and if not, this is the time to move it. Using the stops in the gear box are more accurate then the steering stops on the axle. You should also find the center tight spot when checking this way.
Joe
