I've searched around and haven't found a whole lot, so I figured I would see what you guys have to say. This only happens under moderate to hard braking when the car is downshifting into first, and usually only on flat or downhill grades, never on uphill. Is it the rear end failing to catch up with the transmission? Inside the car you can feel a definite push from the rear, not so much slamming forward but it's noticable when it does it and it sounds a lot worse than in the video. I haven't heard it from outside the car and I know these cars are notorious for amplifying any noises.