Suspension problem
1995 Buick Regal 6 cyl Front Wheel Drive Automatic 99100 miles

I am getting a clunking/squeaking noise in the rear of the car. I have had the rear subframe crossmember, rear leaf spring, rear struts, and trailer arms replaced by a certified mechanic and still I am getting this noise particularly when I go over bumps or imperfections in the road at slower speeds and backing out of my imperfect driveway. I have spent a ton of money on my car and still the problem persists. The car runs and rides just fine. This why I am willing to put money into it. I don't, however, want to keep dumping big money in repairs that does not solve the problem. I am trying to keep it running as long as I can. It shows it age though. Any suggestions as to what may be causing this problem?