There is an adjustment on the engine side of the box. It is very similar to the adjuster for the valves, a slotted screw with lock nut. You may be able to adjust it some, but it sounds more like the bushing is worn. I'd replace the bushing and seal at the same time. Play at the bottom of the pitman arm is more likely a drag link problem. There rebuild kits available for the original style link, or you can replace the entire part.
