i have a 2008 and have those noises also - took it to the dealership and they ordered a new tranny for it, however, when we took the car to have it replaced they informed us that Nissan said not to replace it, that it is a fixable problem and that they are working on a solution.
i drive 25 minutes each way on the interstate 5 nights a week (graveyard shift) and it worries me that something is going to "fall out" while i'm doing 70 on the road at night.