Most times it´s not in the steering box. What you should do is to get a freind to turn the steering wheel left and right a couple of inches and check each joint in the steering parts closely.
Play is usually in the trac bar, sometimes the tie rod ends, sometimes in the steering column U-joints, sometimes the steering box itself.
Trac bar upper joint is usually most of it. Steering box will usually start leaking a little fluid near the pitman arm when the sector shaft gets loose. Proper adjustment, isn´t easy, just about have to remove the steering box to get it right and even then it´s a pain. I did it once and tightened it a little too tight and almost crashed, now I order a rebuild.