Meh Vette

So long story short my passenger NPP muffler is rattling something awful internally at low RPM 1200-2000 RPM. Is it worth trying to get it cut open and repaired or just buy a new set and have them put in? If it is worth repairing, does anyone know of a shop in Houston that will do it and at what cost? Based on the threads I have read this is a common issue for boosted cars to have.

Rky Mtn C6

You may want to check a Corvette repair shop and see if they have any take off NPP mufflers lying around. Could save you some money.

madmatt9471

The repair should be pretty easy and the NPP is easy to cut open and inspect as well!

If you find a good muffler shop they should be able to do it for you with minimal cost.

IMHO - If you decide to go a different route, then one of the best "Replacement" options would be to go with B&B Fusions Bi-Mode exhaust mufflers to keep the quite and open when you want them (plus they work with the stock NPP controller) or perhaps another set of NPP used or go with the Bi-Mode 3" from a ZR1 or Z06

Thanks,Matt

Meh Vette

Did some searching and there is a shop down the street from me that will do the muffler mod and repair/reinforce the existing mufflers. The shop is called TEXAS QUALITY EXHAUST SYSTEMS and the guys name is Roger. He seems nice and seems to know a lot about these mufflers. I will be getting them repaired next week and will let you guys know how its turns out assuming it interest's any of you.

blh

I had this problem as well. In my case, the rattle was caused by the linkage between the NPP butterfly valve and the vacuum-actuated switch. You can easily check to see if this is the cause of the rattle by pressing against this linkage with a *gloved* hand while the engine is running and making the rattling noise (the linkage is just above the butterfly valve). In my case the rattle stopped when I pressed against the linkage. GM replaced my entire muffler under the bumper-to-bumper warranty but I would guess that in many cases, this noise (if the linkage is causing the noise) could be eliminated with some light bending or other slight modification of the linkage. Just a guess though. Also, my car is a stock 427 convertible.

Funny thing. When I first took the car in, the tech noted that I had a Mild-2-Wild switch installed and reported this to the service manager while he was in a meeting with corporate GM. The corporate GM guy said that it sounds like I had modified the exhaust system and strongly suggested that the claim be denied. The service manager was pretty reasonable once I explained what the Mild-2-Wild switch did and they replaced the exhaust in the end.

Meh Vette

No such luck here, I checked playing with the valve and the sound was unchanged. If you pop the side of the muffler body itself hard, it gets quieter for a while and then starts right back up again.

blh

You probably already tried this, but I could never eliminate the rattle by pressing on the valve (no matter how hard I tried). However, when I pressed on the linkage rod on the top of the buffer, it went away. Still, it sounds like you have already verified this. Good luck with the repair.

Meh Vette

I did indeed try messing with the linkage, even tried applying pressure on the linkage from the bottom with a screw driver. I appreciate any advice someone can give me though, you never know what will help you if you don't ask. Hopefully it will all be fixed soon as it is very annoying, first time I heard it I nearly had a heart attack as I thought it was my transmission.

dpigguy

If your repair. Doesn't work, call Corvettes of Houston on I45 North. They may have a similar unit they removed when putting an aftermarket system on other cars.