My truck is a 04 2500HD with dual dynomax bullets all the way out the back. My truck only has 7k miles on it and i started it up today and its making a loud clang clang sound. It sounds like something is vibrating real hard or something. I got under the truck and it sounds like it is coming from the exhaust but im not sure. What could this be? Could one of my cats gone bad or something? My exhaust has been fine untill now but im not even sure if thats the problem. The exhaust sounds normal besides the clangy rattle noise. Anyone know what this sound is?

 

wobble your exhaust tips a little bit and see how much play there is in them. my brothers truck made those same noises you are talking about. one of the pipes hangers came undone a bit and caused that rattling noise. 10 dollars later and a few tack welds and it was good to go.

todd

 

We have had some trucks in the shop with the catalytic converters making a loud metallic random knocking noise. The noise would be coming from the exhaust where it runs under the transmission bell housing. If you didnt know the sound you would swear it might be a cracked flywheel or somthing in the trans itself making the noise. This is usually on higher mileage trucks though, havent seens the cats go with miles as low as your yet, but it is possible.