I have a 2006 XLE Limited AWD: having the same problem. Took to local shop they say the transaxel and transfer case need to be replaced at a cost of over 6,000. They also said front right wheel bearing needs to be replaced. Took it to my local tire shop had the tires rotated and had them check the front bearings and they say they are fine. will now take to dealer. By the way i have 89,000 miles on it.
hope it's not the case but will let you know. Leon
hope it's not the case but will let you know. Leon