Was wondering if you have figured this out yet? I am having a similar issue.
May, 5, 2009 AT 7:51 AM
The Chevy Dealer said it was the center support bearing. It can be greased or replaced. To replace it is at $800. I chose to have it greased. They said it could last 1 day or several years. However, they did not grease, they used oil. I have a personal mechanic that inserted grease with a small tool. The whining has stopped.