When I drive the car, starting at about 35 to 80 mph, I get a harmonic cabin vibration for about 35 - 40 miles. It even happens on a newly paved 6 miles stretch of brand new highway. It begins to dissipate the further I drive. On my way home I get no vibration or its very faint no matter the route I take. Started about 4000 miles ago with no changes made to the car. Car has 31,000 miles new tires with 10000 miles on them and the rims have been check for being out of round by dealership and re-balanced the tire twice. It driving me nuts? Transmission Mount? Flex Disk? Any suggestions?

no faults found when scanned, all the controls inside are working correctly, has the a correct charge of freon, has no power at the a/c compressor when checked with a test light, do have power on the red/white wire on the high pressure switch.