there is clunking on the rear rt/lft sides of the vehicle when I go over a bump

What is your question?

I have changed the shocks and the shock bushings, and there is a huge clunking sound almost every time I go over bumps. It is not always present, and I had a mechanic look at it and he said that it was the suspension knuckle bushings, but I am not sure if its that or a sway bar link or bushing or a trailing arm bushing or a stabilizer bar or even the control arms or bushings. I have put it up in the air at least 4 times at the shop, and its costing me a lot of money each time. They don't really know what it is. Do you have any ideas?

What makes this problem better or worse?

when it goes over bumps at random times

How long has your 2005 Pontiac Montana had this problem?

4 weeks