Originally Posted by Chevrolet Customer Svc
I'm very sorry to see all of you who are having issues with these vibration issues. I have escalated this to my technical department once before and the answer I got back was that for the V6 vehicles it could be the tires or the wheels (or a combination of both) or aftermarket accessories (and other things of that nature). For the V8's it could be the AFM and those problem parts for the V6 as well. This is not a definitive list of possibilities. I would suggest getting your balance and alignments checked to make sure there isn't something wrong with the way the vehicle is setup. Then I would move on to some of the other things on the list that may be suspect as well. Once again I'm sorry to see so many of you having trouble with this and I have checked multiple times and have been unable to find any kind of documentation that would suggest there is an issue with the vehicle outside of what I've given you here.
Jeff Morris, Chevrolet Customer Service
Thanks for the reply Jeff,
I will take it in and have the balance checked. My vehicle is completely "as delivered" stock, 2SS manual, so no AFM. The vibration is relatively high-frequency, and feels more like drive-train than wheels/tires to me, but will have it checked out. The 4th gen cars had a bit of an issue with some slightly out of balance drive shafts that caused a very similar behavior, so I'm wondering if it could be related to that. It seems to change slightly when you push in the clutch and coast.