I'ev been through some of the cheaper stuff already (i.e. tires). I just had a new set put on that were fully balanced and am still experiencing the vibration. As far as I know, the driveshaft has not recently had maintenance...I've owned this Jeep for about a year now. The only component that's associated to the driveshaft that I know has been maintained recently is the differentials (which, by the way, are leaking oil from the seals).

Some information that might help is the fact that above 60mph I can hear (I feel silly doing this, but) wommm wommm wommm vibration that sounds like it's coming from beneath the center console towards the firewall. The harmonic noise stops when I take my foot off the gas pedal.

Any additional ideas?