Hey everyone, new member here and have a question about an annoying rattle on my 2017 Silverado 1500 WT. It only does it when cold and last for maybe 10 seconds and quits. I can't seem to pin down what it is or exactly where but seems to be under the truck about the back of the trans area. It sounds like a metal flap opening and closing kind of fast but gradually get quiter over 10 seconds. It doesn't always do it either but just about every day when i'm warming the truck up before i go home it does. When warm it never does. I've checked everything i can see and nothing is loose (or i just havent found it yet) so hoping someone else has had this issue and can shed some light on it.
Thanks in advance for any input

 

look for loose exhaust heat shields

 

That was the 1st thing i looked at and all fasterners are tight and it doesn't move or is against anything. This rattle is the exact same every time and quickly starts getting quieter and gone within 10 seconds

 

what else did you check?

 

I have a 2017 Silverado that had this. It was the inside of muffler. There is some sort of baffle that gets noisy but goes away once it gets a little warm. I upgraded the muffler to a flow master with a little better sound and the noise is gone. Truck sounds better too. This is my guess. I’d take it to a muffler shop and I’ll bet they will tell you the same.

 

So shaking/bumping the exhaust system should confirm that fairly quickly

 

It may but I couldn’t reproduce the noise when I tried with my truck. I called a muffler shop and they said it was a common issue inside the factory muffler. Replaced last year and no more rattle.