Rear end vibration

[Show5Over]

Hi guys, looking for any advice regarding a rear end vibration. I recently had a diff upgrade done (4.1 gears and a torsion/torque worm LSD). While driving back home I noticed a vibration while driving at 85-100k/hr. The next weekend while driving the car around the block the gearbox decided it had had enough (this is another story), short version - had the gearbox replaced. Vibration remained. Took the car in for a wheel balance - vibration remained. I've had the tail shaft balanced - vibrations still there.
I've spoken to the guy who did the diff, reckons it's not the diff. So what's left? the drive shafts? Or is the diff guy full of it and stuffed the job up?

 

[SavVYute]

You've tried swapping the rear wheels to the front to see if anything changes?

 

[Show5Over]

It never occurred to me. Since they've been balanced, I would have assumed that wouldn't be the issue. Plus I'm running staggered wheels.

 

[greenacc]

If it started the day after the diff was done, Yep probably the diff or something disturbed during the diff job. Can you tell if it's coming from one side or the middle?

 

[Show5Over]

It's too hard to tell. But, it does go away under acceleration.

 

[_R_J_K_]

Disconnect the tail shaft and rotate it and see if it changes.