First, check all the tie rod connections and make sure they are tight. That is at the front where the two tie rods are connected to the steering arm and at the ends where they are connected to the steering arm at the wheels. If any of these are loose, they are adjustable by removing the cotter pin in the end of the joint and tightening them up. Tighten as much as possible and then back off to the next cotter pin hole and reinsert the cotter pin. Make sure everything turns ok after doing this, because sometimes the ball is worn and not round and things will not work if you tighten completely up when the wheels are straight ahead. Also as Vern said, check the big nut under the steering box that holds on the center steering arm. Sometimes that gets loose causing play. If all that does not do it, then drain the oil out of the steering box and remove the big plug in the front of the steering box. That's the one that has a large hex on it to apply a wrench. When you get that out, you can screw out the worm gear enough to check the ball thrust bearing that is on the end. If you want to take the worm all the way out, you will have to remove the steering wheel. If the thrust bearing has any play in it, replace it. You can get a bearing at a Case/IH dealer or probably a bearing supply house or NAPA. Take the cotter pin out of the castle nut on the steering shaft remove the nut and the bearing will just slide off. If that does not fix things to your satisfaction,then you are in to a major rebuild of the steering box. The worm and sector gear may be worn, or the bearing that supports the steering arm shaft may be worn. Good Luck.