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Discussion Starter · #1 ·
Hello i just bought a 2003 gmc sierra. and after driving it for a few days i started to hear a high pitched criket like sound coming from the muffler... just wondering if anyone could give me some ideas on what it could be
 

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heat shield somewhere in the exhaust system.

a loose bolt somewhere.

How do you know the sound is from the muffler? Under what conditions does the sound occur?
 

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Discussion Starter · #3 ·
well i only hear it when the truck is stopped cause otherwise the engine is to loud to hear anything. if i start the truck up i dont hear it. but if i turn the air condition on and put it on high it starts.. but its not the air condition cause i can leave that off and just rev the gas and then it will start..

i figure its the muffler cause when i get out and listen for it you can distinctly hear the sound coming from the middle of the truck.. like around the muffler area.. a couple of my buddies listend to it and they thought it was the catalytic converter
 

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So you can only hear it when stopped, which probably eliminates most suspension components.

Loose heat shields on the catatlytic converter (or elsewhere) would be one possibility. Have you climbed underneath to see if you can see anything loose? Can you get underneath with a stethoscope (or long screwdriver) to see if you can pinpoint where the noise is coming from?
 

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Discussion Starter · #6 ·
ok well i started it up and tried everything i mentioned.. then i took it for a drive... 20 minutes later still no sound... i dont know if last nights rain had something to do with it but the sound is gone for now
 

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ok well i started it up and tried everything i mentioned.. then i took it for a drive... 20 minutes later still no sound... i dont know if last nights rain had something to do with it but the sound is gone for now
Maybe a little piece of the converter matrix broke off internally. Sounds like what you describe.

Happened to me once in a car I no longer have, floored it, kicked it down, and you could hear that little piece rattle through the converter, through the muffler, and probably fired out the tail pipe....

problem resolved.... :lol:
 
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