can the NPP "rattle" be fixed???
 

I recently bought a set of used bi/mode mufflers for my 2008 base coupe. (the stock mufflers are super quiet)
I believe they are off a Z06, (based on the cut an reweld marks on the sides of the cans that look like the Z06 muffler mode i have seen here on the forum) but they bolted right up. So i thought, great! I am good.

However, when i cranked the car, there was a terrible 'rattle", the muffler guy looked around and said "it's the baffles". Closing the baffles manually with my gloved hand did stop the noise. The noise is awful at idle, it can be heard inside the car with the windows down. While driving, the road noise drowns it out, but I assume it is still rattling. The seller says they never rattled for him. Maybe something changed when I hauled them home in the bed of my truck?

I had the NPP in a Box installed, hoping that closing the butterflys with the vacuum would make it stop. No luck. they still rattle. It is even louder since the exhaust noise is less.

A search on the forum gave several threads on this topic.....mostly they just say "ya, this happens" (wish i had saw this issue before I bought them, lol).
Honestly, it makes the car sound like something is about to fall off a junker. I will be embarrassed to have anyone hear my car this way. If I can't fix it, they have to come off (and I am out @800 for the mufflers/controls/install)
anyone have an idea to stop the noise?

You can cut them back open and have the mufflers tacked around the inside and seal them back up.

I had purchased some and had a shop do the mod, it rattled badly due to poor quality work. I cut them open and spent two days grinding off the bad welds. I made some pipes and new SS covers for my welder to put back together, night and day difference. Not really that hard to do.


Good luck!

thanks for the reply.
I was hoping it would be something simple and easy (and cheap!)

There is also another rattle possibility besides the baffle. It has to do with the butterflies, and this is a cheap easy fix. There is another recent post with a pic of the fix for it.

I crawled up under the car and it does seem the rattle is in the can body (as opposed to in the back where the butterfly is).
I called the muffler guy who put them on for me about opening them up to fix whatever it is that is loose inside. He said "no can do, wont be about to get them welded closed because the skin is multiple layers of metal".
anyone know an expert welder in Charlotte? LOL

If he does not want to weld them back up, then maybe someone else would do it. It is not multi layers of metal.

- I made new panels out of SS I purchased from mc master Carr.

- I cut open the mufflers with a cutting wheel.

- I filed them smooth.

- I cut and shaped the new panels a little at a time util they were perfect.

- Then I had my welder weld everything up.

Maybe you could post this in your region with a question of who can do the muffler mod.


DJ

thanks DJ, good idea

Did you see this post: https://www.corvetteforum.com/forums...m-baffles.html

Check out the picture of the cracked seam in the second post .... don't know if that might
be what you have.