Yes threw it in neutral with no change. Even shut off the van lolGenerally, vibration is only caused by rotating components (the only exception being death wobble, but minivans don't usually have that problem...). A suspension issue can cause a bump or shudder, but not a continual, speed-based vibration.
Have you checked or replaced the wheel bearings?
When you had it in N at highway speed, I'm assuming the engine speed dropped to idle ruling out the engine as a culprit?
I don't want to go down the rotor rabbit trail, but just to make sure, have you checked for a seized caliper? That would be the only way the brakes would cause a continual vibration that doesn't get significantly worse on braking.
Sorry if I missed any of those earlier in the thread.
The wheel bearings looked fine with the axles out. No grittiness.
I am not 100% sure about my front calipers...the passenger side does seem to get more brakedust than the driver side, it's been like that for years. Brake fluid is clean.
I don't get any pulling when braking (or notice) or any visual signs of failure. I do want to replace the calipers as a preventative maintenance item but with OEM only. I see some reman ones but I don't trust them. Any have experince with raybestos or cardone reman calipers?