I have the exact same problem in my 2010 4.6 as described by tarche, which thankfully duplicated when a service tech from the dealer drove with me earlier this week. they wound up replacing the entire driveshaft assembly. I pick it up tomorrow and will report to the forum if there is not improvement. other threads on the forum addressing the issue report that Hyundai actually beefed up the hardware of the driveshaft following the TSB of May 2010, to the point where it may have solved the problem entirely. or not.. My vehicle was manufactured in March 2010, so it would have had driveshaft 1.0. Prior to taking it to the dealer (who has been great by the way) I asked Hyundai of USA if they did indeed beef up the driveshaft following the TSB. I got the bigtime brush-off. Anyone with this issue should bring it to the dealer for this fix, and not live with the substandard aspect of an otherwise terrific vehicle.