I know this has been posted on this site in various manners in the past, but I am still having issues with clunking noises likely associated with the differential in my 2007 Z06. Last year, I took it to my local dealer and after a week of them trying to fix the exhaust or loose parts underneath, I showed them the post from this site that suggested replacing the original differential fluid with the new GM fluid that included the stabilizer additives. Once they did that, it cleared right up. This spring, the noises are back and even worse than before. I had the fluid changed again and did figure eights day after day tring to get it work into the differential clutches. It only makes the noise when making right turns and it really does sound like something is hitting the rear undercarriage. It does not seem to matter if I am accelerating or coasting out of gear and it is loudest when the road is a little uneven. Unfortunately, my 2007 only has about 7,000 miles on it so I assume this may be adding to my issue. I also have struggled to find any dealers in this area capable of knowing or checking with someone who knows about the Z06. Each time I have to show them the TSBs and posts from this site to get them to fix the right thing. I even had to teach them how to lift the car and how to change the oil. I have seen various suggestions including loose sway bars and the need to replace the diff. clutches. Any advice would be appreciated.