Deaver Spring Drive train noise / hum 75 MPG

I recently upgraded to a heaver Deaver spring with added about 1.5 lift on the back. I am getting a low frequency notice/ hum/ friction only during acceleration from about 65 to 75 MPH. I can also feel the steering wheel vibrate due to this vibration. Before installation of springs this noise was not there. The shop that installed them could not find a problem and said the springs are "still settling down" The shop that installed said they had the drive line measured and it was all good. I am still getting the noise and I can't imagine this is good for the drivetrain long term. Any ideas?

 

If you feel it in the steering wheel, its something attached to the steering wheel

 

have you checked your driveshaft? I've seen them hum and vibrate before. Pull it out and drive in 4wd and see if the noise goes away. Another thought would be pinion bearing.

 

Driveline/pinion angle. Rule is one degree shim per inch of lift. First try carrier bearing drop. Easy install.