Might as well come back and start posting again so we're in this together. I too picked my car up in a slight rain when I posted my last message. The hum is NOT gone.
I figured out the very next day that it's still just as bad when the rain cleared up. It now occurs at a slightly higher speed (50 mph to about 63, used to be 45 to 60). That may just be due to parts wearing, as my vehicle now has 2300 miles on it as opposed to ~1400. I called Ford Customer Service and reported that the hum was still there first because the dealership said it was gone. The dealership continues to shrug off the problem and will only do what Ford tells them to do. The only person who seems to care is the service manager, but he has no idea what to do.
I'm so over it. I'm just going through the motions until I eventually have to file a Lemon Law suit. I brought the car back this Thursday to have the Service Manager ride with me AGAIN. Yup, problem is still there clear as crystal. They contacted the Field Service Engineer again to see where to go from here. Now I'm waiting for a response. Funny thing was he was about to start a whole new case. Then he thought out loud, "Nah, should probably call the Hotline with the same case number to get a quicker response". I certainly f*%&'n hope so, the problem was never FIXED, still have the same damn issue!
I bought a new car for peace of mind. My new car has spent more days in the shop than the 98 Jetta Turbo Diesel that it replaced. This sucks so bad, I just know this will end in me having to be the a$$hole asking for my money back or a replacement under lemon law.