Your DII can go 75-85. Who knew?

One way to address the problem would be to not drive faster than 74 mph. 🙂

 

If you aren't doing 80 on the interstate down here you'll get rear-ended

 

Have you swapped the tires front to rear to see if the vibration follows

 

I will do this next I was concerned the steering damper would mask things if moved up front but I guess it should make a noticable change even so

Will report back after rotation

 

Has it ever been in a front corner collision? I had one that acted similar due to a slight kink in the frame.

 

I had a chevy truck throw a ring gear tooth once, immediately started whining like crazy. Bought a non-driving disco once where the middle shaft in the transfer case had the retaining ring come off and the shaft walked out until the gears were grinding I would check your differential fluids as well as the transfer case fluid, check the rear diff flex joint. If none of that checks out drop your diffs one at a time and check the gear conditions.

 

Update and resolution. Found a really good tire shop with a road force balancer to really check tires and rims. Found a bent rim that was hard to see unless spun at just the right speed. Swapped the rim with an extra I picked up and now she's smooth as glass.

 

Thanks for the follow up, good to hear you found it and not too serious.