Flowmaster Problem

[Arsenik111]

I just put the american thunder system on my 2001 silverado 2500 and i have a problem. Right now its not welded and there is exhaust leaks,but when im driving normally and it drops down to low rpms it makes a loud obnoxious humming sound and i want to know if this is due to the leaking exhaust and that there is not enough pressure going through the muffler?

[jeverett]

If I had to bet, your just hearing the interior resonance of the muffler. My 40 series does it real bad.

[red00lght]

Yeah...

I have an extended cab Silv and with both the Flowmaster and even the Magnaflow, the humming resonance was just too annoying for me...not to mention it felt like the truck lost some low end performance. I ended up going with a quiet hi-performance muffler (don't know the brand)splitting to dual exhaust out the back and I'm very happy overall. No resonance inside, but yet a nice aggressive sound when I punch it. I wish the truck was a little louder, but I understand with extended cabs, you get resonance very easily with aftermarket mufflers.

[rustcal]

hay red00lght do you think you can figure out what brand muffler you have? I have a 00 silv with FM 40 series split rear and the interior noise is really annoying. Thanks.

[red00lght]

Rustcal,

I will look under the truck tomorrow to see if there is a brand name listed on the muffler. I'm just happy to be headache free and have my performance back with a little V8 rumble to boot.

My old Lightning loved the Magnaflow and it sounded great, but my 4.8L Silverado felt like it lost 20hp and the noise drove me crazy. I guess I'm getting old!!!

[kenny-1907]

Hey red00lght, I was wondering how long you had the Magnaflow muffler on there before you switched because of the power loss. The reason i ask is because i have a 2000 Silverado with the 4.8 and when i had duals installed with Dynomax mufflers i noticed a big power loss, drove it like that for a bit , had the truck checked out and the techs said that the truck had alot of power but it felt like something was holding it back. Long story short, i had the spoke to the muffler shop and they removed the Dynomax mufflers and installed a set of Flo pro's......with the same result......untill after about a month's worth of driving, then the power started to come back. The more i drove it the more power came back. I have talked to a few other people and they said that the had expierenced the same problem. I am now quite happy with the sound and increased preformance in my truck. Some people say that it will take maybe 100 miles or more for everything to adjust to changes such as Exhaust or a cold air intake.........just a thought.

[red00lght]

Kenny,

That may well be the case. I only kept the muffler on for a week before I swapped it out.

But, I also put two Magnaflows on my Cadillac DTS (don't ask...) and had them on there for a year and never did get the power back. When I put the stock ones back on just before I sold the car, it felt alot stronger again. Maybe the truck computer responds better over time...or maybe you are just used to the way the truck feels so you don't notice the loss in power?

[kenny-1907]

I had the dynomax mufflers on there for about a week and the day i was on my way to the muffler shop to have them removed and flo pro's installed , it kinda seemed to me that it was getting a little more snap to the throttle. But that went away as soon as the flo pro mufflers were installed. The more i drove it , like i said the more power came back. Like i said in my earlier post , i have heard that some modifications take time before you start to see any benefits or increases because the computer has to adjust to the changes. That is sure what it seems to be with my truck anyhow. Just a thought.