2007 Ford Fusion AWD Rearend Sound?

I have a 2007 Ford Fusion SE AWD with 3.0L V6. It has been a great car. As of now it has roughly 78,500 miles. Recently I have been hearing a sound from the rearend. It sounds like your going over rumble strips, like on the side of the highway but it's MUCH, MUCH more quiet than that. The slower you go, the slower the sound is. The faster you go, the more intense the sound is. It is very noticeable. I figured I would get some insight from others before I take it to the dealer. I feel like it's probably a bearing or something in the differential. It doesn't seem like the rearend is going bad. I had a 2004 Explorer (worst vehicle ever FYI) that had a bad rearend, and the rearend would just "whine" during acceleration. Also had a 2010 F-150 with the whine. Starting to think Ford can't put a good rearend in a vehicle! I now own this Fusion & a 2012 F-250 for personal use. And I have a 2011 F-350 for my business. Just thought I would throw that in there. ;) Any ideas? Thank you!