tonipmct

I have a 2007 Ford Fusion 3.0 AWD with about 68k miles. Two weeks ago began a strange whirring type noise. Noise only happens upon acceleration and the noise gets louder the faster you go and gets quieter as you slow down. It is hard to describe the noise. I was thinking possibly a wheel bearing but noise sounds like coming from center of vehicle???? Rotated tires and no change. Noise is not present when car is at idle, only when accelerating or deaccelerating. went to Ford and was told it was Transmission and Transfer case but they werenot certain. Trying to get some ideas here?? any ideas from all you fellow Fusion owners?? any help would be greatly appreciated. Noise is getting worse since two weeks ago thanks Jeff