You mentioned that "it's no longer smooth". Does that mean it was smooth when you first got it? Really, the only thing that could effect it is the tire preasure, as navigator3740 said, or the shocks. Is it possible somebody replaced the shocks?
The reason I haven't gotten to it is because I spend too much time detailing it! Just no time to do what should be done, but plenty of time to wash & wax, bleach the whitewalls, apply silicone to the rubber, condition the leather... but God it looks grand!
The ride is to die for! Sorry yours doesn't suit you remo9344. I know just what you mean. I took my wife's '99 G. Marquis on an errand this morning... ugh. Corners like it's on rails, but that ain't worth much to me. Too stiff! If I had to drive that all the time, I'd drop the tire pressure to 24lbs or something. I'd sacrifice tire life for a better ride any day!