Need help ID'ing a sound...

[MrShanks2U]

Ignore the video part...it was dark outside. Its the rattling noise. This video was shot from underneath my truck, parallel to the muffler.

http://www.youtube.com/watch?v=ISIx6m4bO68

{wait for it...}

 

[Viper Command]

sounds like a rod knock, or heavy detonation.

but wait for big jim to jump in.