Differental Problems

Have had my new Expedition in the dealer shop three times in 30 days. Grinding and vibrating when turning in front wheels. Dealer says ford is aware of this common problem and that they change out 3 to 4 on expeditions a day! Why does not anyone else complain about this? Everyone I run into with a 2004 exp. complains about the same or worse problems. My car didn't even have 500 miles on it when the problem started. If this is so common then why hasn't ford fixed it at the manufacturing point? Anyone else have this problem? The dealer has done over 3,000 in repairs so far, all under warranty.

The grinding and vibrating is probably not from your differential(s).
We ran into this on some of my fleet vehicles with automatic 4X4. The viscous clutch that drives the front wheels is the source of the noise. Change the transfer case fluid and refill with synthetic fluid.