My truck, 2013 crew cab, 4x4, a little over 100k miles, fully dlt'd for about 10k miles, has recently developed a hum like vibration that can be felt in the floor pan and pedal most prominently over 70mph. More like a buzz you can feel. No noticeable sound or noise associated with it. no codes, no other known issues. I am way over due for brakes for full disclosure.
I don't see anything physically wrong, but have not removed the wheel to see. it really feels like a tire issue, but no bouncing no balance/alignment issues otherwise. Tires are only about 12-15k miles old (BFG TA KO2's in 35x17's... normally very quite tires) and have been rotated at least once before. Also if i'm on a curve at those speeds, i can feel it diminish or completely disappear. when i straighten back up, it comes back.

What would you troubleshoot first?
Brakes
Hubs
Drive Shaft
Tires
What else?

I'd rule out exhaust vibration as it does not appear to be RPM dependent, but only speed. and nothing has changed on that end for the last 10k miles. Could the brakes cause this? Anyone seen this before?