Thanks for all of your help

 

Thought your original post said the differential had been rebuilt. My first diff rebuild I did myself, I had to tear back into due to howling, and a slight vibration, not a bed shaking vibe though. I was thinking possibly a bent axleshaft just from some things I've seen being a Millwright. i deal with a lot of pump shafts and blower shafts. Seen some odd things from a mild twist in a shaft. Wish I could be of more help. The only other thing I can think of, which I'm sure is not the issue, would be flat spots in the tire. My ABS is shot on my 07, had to lock the brakes up a couple times, my tire balance is spot on, but those flat spots rattle the entire truck.