is it when you're driving? or when you are just idling?... If you hear it all the time (idling or driving) it's your fuel pump. That's the only thing in the rear of the car that will make any noise all the time. Stock pumps make some noise at the end of their life. If you only hear it when you are diving, it's the rear end. might wanna have a mechanic pop open the pumkin and see what's going on in there.... good luck
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