Georges…
When you say you changed the U joints, you mean the ones in the steering shaft area, right?
If I recall correctly, there are either two or three total, one (or two) in the pilot’s cockpit, and one joint where the steering shaft goes into the rack.
A quick test would be to sit in your car in the garage, and turn the steering wheel left and right to see how much play you have without the wheels even turning.
If you’re detecting a lot of play, then have someone watch each one of those U-joints individually to see which one of them (if any) is the problem.
If they are good, the next might be to put your car up on your 4-post lift, so that the front wheels won’t turn, and do the same test.
This time, watch the input shaft to the steering rack. If the movement occurs there, then the issue is in that part of the steering rack.
Just a slow process of elimination! Keep us posted!
Rocky