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BiggRob77 9/22/2012
2007 Hummer H3 Base 5Cyl3.7L - Transmissions & Drivetrains
Loud annoying metal rattle under truck.
It sounds like a heat shield for the catalytic converter but I'm not sure. This rattle happens ONLY between 15mph and 19mph. At 20mph it's totally gone. Also it rattles between these speeds whether your accelerating, decelerating, coasting in gear or even in neutral. It must be some sort of shield but maybe someone else has had something similar so I figured why not throw it out there and ask. Any clues???
1 Answer
  • CVO
    CVO 9/22/2012
    It sounds like a heat shield for the catalytic converter or the honey comb inside the cat. If it is the cat, this vehicle is still under the warranty for 8 years or 80 K miles.
    BiggRob77 10/6/2012
    Thanks. I was thinking that myself but it has odd times when the noise happens. I would think that if I was to rev the engine that shield would rattle or make some sort of noise but it doesn't make a sound. I will have crawl under it this weekend and bang around.

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