Unfortunately, Ford has a major problem with having this problem in the rearend. My '04 Explorer had that problem and our Service manager, who is the top in the state (he has taken all the mechanic tests and more tests and passed them all), told us that the only way to solve the problem is to replace the rearend. He said just replacing the bearings does not fix the problem. My husband's '05 mustang had the same problem and he traded it off after this was his 3rd problem with less than 1000 miles on the car.
I am so glad you got your stang fixed. It is so nice to hear that.
Tammy