popping noise from frame rails

[HummerN23]

Not quite, it is very loud, especially after shutoff. when walking through a large 1500 car parking garage you can hear it at the other end from where I park. seeing how it is one of 1500 doing it, I'd hardly call that normal. I can even hear it when stopped at traffic lights. You should see the looks on people's faces when they are stopped next to me, drool dribbling down their chins, when they hear 'POP TWANG".