I posted a topic on getting water in my rear differential, and I replaced the fluid, but after that it starting having a scrubbing sound around corners meaning the limited slip is grabbing more then it should. I took the truck in to get it warrantied, and they voided it due to the very little amount of water that was found. Before I replaced the fluid. Stupid me, I took it in there to get them to check to see if there was water in there. For people saying that the rear diffs are very difficult to get water in, that is very untrue. Have you ever checked to see how the vent is routed? It's very easy to see. On the driver side rear wheel well, look inside the square tubed structural member that's used to support the loads in the box. About 6"-8" in, you'll see a small nipple surfaced about 1/4", this is the vent for the rear differential. Considering the fact that the square tubed structural member is wide open to the wheel well, I can't see water not getting in there just from driving in the rain! For anybody that wants to see this, I have pictures. I going to take my truck in to another dealer and see if I can get it warrantied there. If not, I'll e-mail the pics to the Ford rep in are district, and visually show how this can happen.