high pitched squeal when going over 55mph

I have the same problem with my Freestar 2006. Check Ford's recall 04v446000 and this link http://www.allworldauto.com/comments/viewthread.php?cid=618504

Have your brakes and cv axles checked, some brake pads come with wear sensors that squeal when the friction material is worn down and needs replacement

I have a 05 freestar and i have now changed both right and left front sealed wheel bearings.They arent hard to change but a little pricey.100.00 dlr range if i remember correctley,I have around 70000miles and they didnt go out at the same time but not to far apart.If your getting a high pitched whistle and it changes notes,turn your wheel and it stops,i would bet money on a wheel bearing,figuring out which one is the trick,but that was definetly my problem,hope this helps,enjoy!!