We have a 2008 Ford Edge Limited. At about 6000 miles we noticed a whining/humming coming from the rear end as well. This would usually occur over 40mph or so. We took it in to the dealership...they took it for a drive and notified us a short while later that this noise is due to a "defective" Constant Speed Plate in the axle of the vehicle. They explained that it is covered under warranty, but they will probably have to replace the whole rear axle which makes me a little nervous. I will keep you all posted on the results.
