Keep in mind it comes out further when the rear axle drops during use.
As for the fix, I wonder if I should post in the Talk forum. It would be interesting to see how many people might be ignoring this problem. The other unit I've driven in town also had some vibration in the rear (though I could only feel it vs hear it.) Seems like his could use a new u-joint or two. And, he's got a 3" lift with links.
The other reason to post in Talk is I originally thought the characteristic vibration of the 6VE1 around 2200-2500 rpms was transmitting thru the drivetrain. I had a whole big thread on the vibration about a year ago. Any repost would serve to resolve that issue/thread.