Last week the rear pinion seal went bad. Took it to Ford to have it replaced. After they "fixed" the leaking seal I started getting a vibration in the rearend around 40mph until about 47 or 50mph. I took it back and the "head mechanic" took a ride. Said, " there is definitley a vibration". They scrathed their heads and put a new carrier bearing in it. Drove it, and that did not fix it. Finally they called and said they changed the driveshaft angle. "It is good". I pick it up; they charge me for fixing a problem I believe they created and now it vibrates worse than it did when I took it back. I hate to give them more money to scratch their heads with.