3" is pretty major play and your box likely needs a rebuild if the rest of the steering is tight. Before you fiddle with the box you should eliminate any excessive looseness in the linkage. The ball stud inside the tie rod where the Pitman arm connects is a good place to start since they are usually neglected. The adjustment screw on the box should only be adjusted just enough to take up slack between the worm and sector. If you get it too tight the steering will bind in corners, not good. Remove the filler plug on the box and check with a small, bright light to see if there's any oil in it. If not, straight STP or Motor Honey will do in a pinch.