I have a 2002 mustang GT Automatic With 18000 miles on it.Yesterday,While backing out of my driveway,I heard a slight popping noise.As I drove on,I heard loud horrible clunking or grinding type noises from either under the car or one of the wheels and it felt as though I had a flat tire.The noise stopped for several seconds then came back again,this time really loud.I pulled over and checked the wheel lugs and tires and looked under the car for any leaks or anything odd.there was nothing.I restarted car and drove away and the noise was gone.Does anyone know what could be causing these noises?I was driving straight and I wasn't using my brakes at the time so I don't think it is my wheel bearings or brakes.