Re: Deceleration Noise
Does it change of the brakes are on of off ? If there when braking first thing I would do is check the rotors for scoring and brake pads for wear. Also I would check the differential fluid (not that I suspect it but a good time to check since I'd raise the car and remove the wheels to reall check the brakes.
If not the brakes, does it change if going around a corner ? Left and right or just one ? (If so I'd suspect a wheel bearing).
Let's start there.