I brought my 09 LTZ in again for this problem just after xmas - dealer replaced drop links (stab bar to shock tower loose - or so they claimed). Still have the strut noise on low speed/cold temp. I don't even need to hit a bump, can just be uneven blacktop - every undulation in the pavement and the struts rattle. I am just going to keep bringing it in when I have time - it's crazy!. I will have to take the tech for a ride to demonstrate the issue I guess. I still am trying to get to the engineer again to see if they found a fix - haven't had a chance to get over to GM Tech center lately. Stay tuned........
I've had my upper mount replaced. Still making the clunking noise, just like you over uneven blacktop or hitting a bump. Same year, 09 LTZ. Out of curiosity, where was yours built? You can tell whoever you talk to that there are other 09 LTZs with the same problem you're having, and would like an answer.
Out of curiosity, what is the GM tech center?
If you get an engineer to look at it, please keep us informed, I would like to go back to the dealer with some information, as they seem to be running out of ideas, and instead of them holding onto my car for 2 weeks changing misc. parts to hope to fix it, it would be nice if i can say look up a certain tsb or something.
By chance, do you also have an issue where the steering wheel doesn't return to center smoothly? Like you can feel a slight pulsation as you come out of a turn? I've had new tires, new steer gear, new steering rack, new axles put on and its still a problem. I swear i think its the tires, but the dealer refuses to believe so, since they put new ones on, but they said they'd look at it. Last time my car was there 2 weeks and it wasn't fixed, and I want to drive my $30k car and not a base model G6.