My Expedition is making a loud screetching/wining noise when it is in 2wd and I excell on the gas and then at a certain speed/rpm it goes away for a little bit. But when it is in AWD, it doesnt make any noise. sounds like it is coming from the front drivers side. I had the bearings checked and they are good. I don't want to take it into a Ford Dealership, but its looking like I will have to, to find out what the noise is. Any ideas?