Well the response I got from the dealer yesterday when I had my truck in was the standard. Tech felt the vibration when I took him on a test drive, but they couldn't find anything. No data to go on. Rang the GM mechanic line and they were told there's no known problem, which is just a joke since so many on here have issue numbers (or whatever they're called) with GM. Anyway I told him, GM does know about it and is ignoring it and that you just have to search the web to find hundreds of references to the issue. Also told him about the AutoGuide article coming out. So driving it home last night, it actually felt worse, so I'll be contacting them again.