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Odd "rattling" Noise..................


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Have an odd noise that just started on my truck this morning. When the truck is idling down from a "rev" of the throttle, it makes a weird noise (like a rattling exhaust) momentarily..Checked the exhaust over, and everything is nice and tight.....Had my wife work the throttle a few times while I was under the truck, and it sounds like something in the transmission......couldn't quite pinpoint the exact location. My tranny hasn't acted weird while shifting, so I'm at a loss...... It isn't a constant sound, just happens right before the truck hits idle rpms................Knowing my luck, it's something going out in the weak-a$$ tranny..............truck is an '03 with around 52,000 miles on it.........Anybody have any ideas? Would greatly appreciate the input...............Thanks!

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Could be a rattling exhaust heat shield. I am no tranny expert, but if something is rattling when the transmission is in park, it probably isn't the transmission at all. There are heat shields above the muffler and near the headers/firewall. I would check those. I have had a rattling heat shield before and I could hear it immediately in the cab.

Edited by KissMySilvSS (see edit history)
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Could be a rattling exhaust heat shield. I am no tranny expert, but if something is rattling when the transmission is in park, it probably isn't the transmission at all. Their are heat shields above the muffler and near the headers/firewall. I would check those. I have had a rattling heat shield before and I could hear it immediately in the cab.

 

I didn't even think about the heat shields near the firewall..........I'll check that out. Thanks for the input... :cheers:

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You might need to pull your inner fenders out to get to them. They are very thin aluminum, so don't be afraid to bend them if they are rattling on top of something. Same with the heat shield around the muffler. Might be touching something just enough to make a rattle! Good Luck!

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Went back out and started the truck.......no noise. Let it run up to temp a little bit, and the noise came back.... :rolleyes: Must definitely be something somewhere with the exhaust. Maybe the heat is allowing something to expand just enough to rattle against something else??? Will definitely check the front heat shields though.......but it still sounds like it's coming from an area past the firewall......ahead of the transfer case. I'll have to get it thrown up on a lift somewhere, so I can see alot better. Thanks................. :D

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Like already mentioned, check your heat shields. Many times a loose heat shield will only show its true colors at idle. That could also be a sign that one of your cats is coming apart internally, my GTP had a similar issue a few years ago. When the truck is warm(but off), wrap on the bottom of the cat quickly with a gloved hand. If you hear a rattle, then its the cat(I have experience with this). Keep us posted. :chevy:

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Very interesting. I have the EXACT same issue. I have an 03 w/ 6X,XXX miles. Because it's been to dang cold in the midwest lately, I just keep putting off actually crawling under there to even poke around. You described it very well.

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Like already mentioned, check your heat shields. Many times a loose heat shield will only show its true colors at idle. That could also be a sign that one of your cats is coming apart internally, my GTP had a similar issue a few years ago. When the truck is warm(but off), wrap on the bottom of the cat quickly with a gloved hand. If you hear a rattle, then its the cat(I have experience with this). Keep us posted. :chevy:

 

Just a lil' update, I did what you said, and sure enough the cat on the passenger side is the culprit. My truck threw a code today...can't get it read until tomorrow......but I'm sure it will show up as the "catalyst efficiency below threshold".......Just wanted to tell you "THANKS" once again.. :cheers: .. and I really appreciate your help. I have a few questions, but I'll ask them in the appropriate section now.............

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Just a lil' update, I did what you said, and sure enough the cat on the passenger side is the culprit. My truck threw a code today...can't get it read until tomorrow......but I'm sure it will show up as the "catalyst efficiency below threshold".......Just wanted to tell you "THANKS" once again.. :cheers: .. and I really appreciate your help. I have a few questions, but I'll ask them in the appropriate section now.............

 

Glad I could help, now get the dealership to replace those cats FOC under the 8/80 warranty. :cheers::chevy:

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