I just replaced the lower ball joints on my 99 Exp XLS 4WD. When I took it for inspection, they found and showed me the drivers lower was sliding up and down in the socket. This is the second time I've replaced them and the last time I did not ask for oversize ball joints but did notice they were really hard to press in. (did it with a tool, but only had a hand ratchet to turn the screw on the press). When I took it out it came out very easy and the new one went in very easy as well.
I measured one of the joints I just took out and it measured 1.760 across the splines.
I know I've seen where some have had this prob in the past but haven't seen a resolution.
Has anyone tried peening the socket to tighten the hole ? If control arm replacement is the only option, I might consider welding the dang thing to the arm. Getting quite frustrated with this vehicle.

 

Not sure this will help much but I've experienced similar issues. I replaced the lower arms several years ago thinking it would be better than just replacing the ball joints. Couple years down the road and the lower ball joints are making noise again. So this time I pressed on some new Moog ball joints. Best I could find and they are now making the same noise. I'm not sure what the fix is but I'm getting tired of all the issues these trucks seem to have as well