OK Im going to try and explain this as best i can. 2002 Dodge Ram 1500 5.9L 4x4 SLT 111000 Miles. Bought the truck last week since purchase replaced rear brakes, fixed washer fluid sprayer, new speakers, rear doors would not unlock fixed that now im have this issue.
I was turning onto the highway today, put her to the floor she what shes got accelerated good/hard tranny shifts hard but thats not my concern yet. with the truck floored there is a vibration/humming that gets louder with the RPMs and it felt like something was dragging. When the truck shifts into OD the vibrations is gone feels 100% normal but the dragging is still there. So i set cruise to see whats happening. The cruise was constantly down shifting and fighting to hold 70MPH. but in tow haul mode it would not down shift but still felt like it was working to stay 70.
Now I looked at universal joints everything looks good underneath Drive shaft nice and tight. Also noticed with some snow on the ground and the tire breaks loose i get almost like a grinding from the rear end only when it spinning she grabs its back to normal.
So idk what to look at Drive Shaft?, Rearend? Could be brakes i suppose but replaced rear disc pads and rotors did not replace the e brake drum setup just loosened them up.

Ideas?