[wilkin250r]

So I put it up on jackstands and pulled the wheels off, and revved it up to 55mph on the jackstands. Same vibration, but it had a different "rhythm" to it. Instead of a bruup bruup bruup, it was a constant bruuuuuuuuuuuuuuuup.

I was by myself, so I didn't have an opportunity to crawl underneath it to inspect at 55mph, the best I could do was crawl under at a high idle, in gear (about 20mph with no load). No abnormal sounds coming from the axle. It's a 2-piece driveshaft and the carrier bearing was recently replaced, no abnormal sounds coming from that, either.

Vibration is unnoticeable at any speed below 35, barely noticeable from 35 to 45, but from there it gets REALLY noticeable and peaks around 55mph. Any image in the rear-view mirrors just becomes a blur. And like I said, significantly higher frequency than the tires, about the same frequency I would associate with the driveshaft.