Around 57k on the truck. Just had the car jacked up and the wheels don't budge. I thought wheel bearing at first but the symptoms got slightly better with the diff replacement. Now they seem to be back to where they were and I'm getting the whistle/whine. I'm hoping its something simple like a wheel bearing.

@Axelander any updates?

Do you know about this?

Technical Bulletin No: LTB00305 (issue 1) dated 13 Aug. 2010
Section: 308 Audible Boom / Vibration @ 2,600 - 2,800 rpm
http://australiancar.reviews/_pdfs/SB-10069796-0699.pdf

No change with mine. I installed that TSB, may have reduced the vibration a bit but did not fix it completely. The hole that the TSB damper screws into is not tapped... so you have to tap it yourself.

I picked up a 2013 LR4 earlier this year that had the same symptoms. I did a bunch of research and found the TSB and ordered the parts and installed myself like previously mentioned. I had to tap the transfer case for the bolt which wasn't a big deal. It took care of most of the vibration/resonation that was happening at those RPMs. Well worth doing IMO.