Very loud groan/droning sound from back end - help?

[desert_porsche]

I guess that was my bad on assuming a failing wheel bearing had to make a screaching/grinding noise!

This evening, I was trying to figure out which bearing it was. I jacked the car up and tried to see if any wheels had any play. Absolutely nothing. Every wheel was very solid on the hub (except for the fronts which have a little bit of steering play anyway). I tried rotating each wheel, and they all seemed to rotate quite freely. None of them made any notable noise except for a bit of the brake pad rubbing against the rotor. Finally after Googling around I came upon a suggestion to try holding onto the spring while rotating the tire. First three tires were perfectly smooth, could feel no vibration in the spring. Finally on the last tire, I felt vibration being transmitted into the spring while rotating that tire.

AT LAST MY LOUD GROANING PROBLEM IS SOLVED! Thanks guys