My prob is almost the same, when the bass hits and the car is off, that is the only time that you can hear it on the outside cant really hear it on the inside, something rattles under the car it sounds like loose bolts kinda, ohh no cars coming apart

, but anyways it seems to be coming from between the gas tank and the bottom of the car, it is really hard to pinpoint even when i get under the car but i cant get to it or see it so i really dont know.
any ideas?
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