I've heard loud gear whine on decel before. What I have now is a bit different. It's more of a slight flutter, like a pigeon. It's louder on decel between 55 and 40 mph, but still slightly present on accel between 40-45. At 50, with accel - nothing, foot off gas - flutter. Not real loud, but noticable.

So I'm wondering - is this gear whine? has anyone else heard gears "flutter"? Could it possibly be the tires, even though it's louder on decel? I've had them rotated - no change.