I have a 2002 HD with 6.0 200k and it has an annoying rattle at about 2200-2400 rpm. Its just when you leaving stop lights and it sounds terrible. I thought it was a baffle broken in my muffler so I put new flowmaster super 44s on it. Now my work truck is a factory 06 HD 6.0 with 60k on it and I notice it does the exact same rattle its just quieter as does my buddies factory 06 with 200k. Now If I plug off the drivers side exhaust it makes the noise stop. Truck has no cats

I read online that the 02 sensors sometimes have a rattle so I pulled them and plugged them off and the rattle still exists. I hope this is a common problem and its easily fixed. Anyone have any ideas?

 

Yes it is common... I had it in my truck as well as my buddies truck. I crawled all up under my truck looking for the source to no avail. I recently pulled my motor, trans, drive shafts etc. After removing the exhaust I noticed the cats had something loose in them like the catalyst was coming out. I plan on cutting into the resonators at a later date to investigate. Going back on with Kooks LT's and their green cats system... If that damn rattle returns Ill be very disappointed!

 

i had a rattle like that on my 99 with a 5.3 it ended up being the solenoid in my starter. the little gear that shoots out from the starter to engage the fly wheel had gone bad and was just sliding out and hitting the flywheel at the same rpms you were at. i thought it was carbon in my cat but really it was the starter.

 

My starter was a brand new factory unit but I will def give it a look before it goes back in my truck. Thanks for the tip!

 

On my '04, the exhaust rattle was coming from the heat shield on the top side of the muffler. One of the welds broke.