car had been at dealer several times for vibration.. had driveshaft flange replaced and balanced shaft TWICE...less than two months later the driveshaft came loose at rear and was banging against the floor before front u-joint broke and driveshaft went "free-agent" on me!..sick of ford dealer..took it to local hotrod shop and they installed an aftermarket performance (steel) driveshaft at around $750.. problem solved no vibration/quiet cabin at 55mph and over... no more dealership visits for me.. I'm off to my attorney's office,though..