Get a partner who can turn the wheel back and forth just a bit past either side of the slop while you look at each component in the steering system. Start at the tie rods at the spindles and work your way back to the gear box. This will give you an idea of the worn parts. You want to pay special attention to the places where two components link together. If the connection is worn out, one of the parts will start to move before the other one follows as your partner changes direction of the steering wheel. This may take a little coordination between you and your partner as to when, how far, and how fast they turn the steering wheel back and forth. A good example is to watch the steering colum shaft turn at the gear box. Ideally the input shaft turns - the output shaft (& pitman arm) should follow immediately. If not, you have a worn gear box. Wear at drag link connections and tie rod connnections should also follow immediately.