I've asked around and nobody else seems to have heard the noise that I hear every time I pull down an exit ramp after driving some distance at highway speed. The sound is a dull thud, like someone hitting a rear quarter panel with their fist. It happens within 60 seconds of my decelerating to a stop. The first time it happened, I thought that someone had hit me. After the first few times, I figured it was just the wing parking itself in the down position, but I ruled that out when the noise happened on a freeway trip where the wing had not deployed. Furthermore, I don't think that it is the gasoline sloshing around in the tank. I'm stumped.

Anytime someone new rides in my car, they jump when they hear the bump. I've gotten used to it, but want to make sure that it's not something that I should have the dealership look in to.