OK, I have a 2004 5.3L Z71 extended cab. Today as I was driving, I started to hear a weird noise coming from the bottom of the truck or from the bottom of the engine. It sounds like a rattling noise, like if there was a wrench somewhere banging around. I stopped, looked under the truck, under the hood to see if anything was loose, and nothing. Then I drove, no sound then like 15mins later, it started to do it again.

I started thinking, could it be the muffler? So I get to work and when I left, no sound but then the service engine light was on, then the sound started again. HOw can I find out if it's the muffler or what is it?????

 

get under the truck and wiggle the exhaust around see if it hits anything....another thing u might try is let it idle and see it the noise starts.. but it sounds like it only happens when you drive

 

Thanks Davey, I will try that, I will also go get the scan codes read?

 

get codes read for sure. does truck drive funny now, or just make noise?

 

It's an 04. Right below your shift indicator is the DIC. When you start the truck, look for any codes or information coming from your PCM. You might not have to get your codes read, you may be able to read them yourself.

 

maxxman04, it just makes noise, it doesn't drive funny, yet...

 

so i have an 04 silverado 4x4 ext cab. i had this problem and thought the problem was in the bottom end. it turned out to be my cat went bad. the honeycomb material inside the cat broke up and sounds like your problem. unfortunately for 03 up its a dealer only item or find one from a junkyard but who's to say that the junkyard cat wont go bad. my problem was worse when the motor was cold and was less noticeable when the motor got to op temp. when the tech at the dealer took the old cat off he dumped it vertically and all the material came out in pieces.

 

good call s34n. hadn't thought of cat. might be just the heat shield to. this is common on alot of vehicles.

 

will the scan code show the cat being bad?

 

jeeze..if u gotta replace the cat.. get a high flow cat.. forget paying what the dealer wants.. lol