These boxes are one of the achilles heels of the 123 cars. I know I am repeating what was said earlier, but go through the ENTIRE steering linkage and don't forget to see that the wheel bearings are not loose.

Check all tie rod ends, drag link ends and idler arm bushings. When you are CONVINCED that there is no problem there, tighten the box as described very carefully. After you loosen the nut, back the stud out until you feel the slightest resistance and HOLD it there while you tighten the lock nut. Do this with the steering wheel in the straight ahead position.

I have done exploratory surgery on one of these boxes and the only way I see to tighte a worn box is with shims. It would have to be done carefully to get out the slack but not making it too tight.

Good luck,