2000 Mustang GT Whining While Turning in Reverse. Cause?

I recently bought a 2000 Mustang GT, V8 - 4.6L with only 90,000 original miles. The previous owner babied it very well. Now, three weeks after purchasing it, I am hearing a whining-like noise when I'm in reverse. It happens as I turn before, during, and after applying the brakes. It doesn't sound like the brakes are causing it, however. It almost seems as though the sound is coming from the drive train.

Can anyone help me with this?