Hey all, first time user/poster. I am trying to gather feedback on an issue I've been having with my 2011 3.7 V6. I have had the 1 piece aluminum driveshaft and 3.73 gears installed at the same time by a local speed shop and they even dyno tuned it.(Shameless brag of 300HP at the wheels. Woot!) Anyway, ever since then, While IN GEAR and OFF the throttle, the rear end vibrates Violently, shaking the whole car, usually at highway speeds but often at any speed as well. The effect is minimal in 6th gear but still there. While under acceleration or in Neutral, there is no issue at all. Did the shop just mess up the install? Should I have the diff rebuilt? I have a friend who runs his own speed shop and he's willing to help but I'd rather get some info before driving 200miles to see him.