Have you tried sitting with the car in park slowly increasing the engine rpm's until you feel when you have noticable vibration (on mine around 1400 then again 2200 or so) which translates into around 75-80 on the road. . The vibration might be engine related transfered to the drive train. Bad mounts would allow this big time Also when you are getting the vibration while driving try going to a slightly higher speed then put the transmission in neutral again isolating the suspension from the driveshaft and engine. Might help pinpoint the problem. Good luck. I had a vibration problem by the way in the rear of my car for about 5 months. Did the balancing thing...Did the new Tire thing.. Finally did the new tire thing again (Michelin preformance) and still had vibration. Drivers rear less than 5k miles started to split on the sidewall. Dealer replaced it with a new one and low and behold no vibration so it's sure possible to get a bad brand new tire. Twice even.