I've got a magnaflow catback (which I do like) but I realized recently that the resonance for the backseat passengers is pretty loud. It probably wouldn't be too bad if I weren't supercharged and living in a hilly area. But I have what I have and live where I live and I'm looking for a way to make it better/quieter.
I've already installed dynamat extreme from the back of the front seats and console all the way to the rear door hatch. I yanked the rear interior and used 36 sq feet and covered every exposed inch of floor area. Road noise is reduced, but I've still got a lot of resonance in the 2300-3000 rpm area.

Any tips on knocking it down some?

 

Crap... I meant to post this in the general truck section... sorry Mods!

 

... but if your muffler is not welded and you can rotate it 90 degrees it MAY help.
A friend of mine muffler resonance made everything in the bed dance and rattle. He rotated the muffler 90 degrees and it stopped and he says it is quieter. I have not rode in the truck myself.

I have a Corsa Touring edition and it is nice in this area.
You may also want to try a resonator like the Dodge trucks have.
The large cabin of a SUV makes for a battle.

 

just get the inside rhino lined like another member did. says it is as quiet as a benz

 

http://www.acousticstandards.com/acousticalblankets.htm

 

This is common for a straight-through muffler design versus a baffled design. Which size Magnaflow muffler do you have on there? I would recommend getting the biggest possible muffler in there (22" or 24" body), that would certainly help. I'm actually welding up two Magnaflow mufflers in series (one 4 x 9 x 18 that is 3" in/3" out, and one 5 x 11 x 22 that is 3" in/dual 2.5" out) because I want the flow of the Magnaflows, but none of the resonance.

 

My truck is undercoated. I've ridden in couple other trucks that weren't. Not with the same exhaust but with similar loudness. Mine is quieter.

 

I was kind of wondering if anyone has added bullet mufflers before the magnaflow and if it made it any quieter? Bullets shouldn't hurt the flow much.

There's no way I can do the rhino-lining on the inside. I've already done the dynamat.

As far as muffler size... I have the 22'' case already.

I considered the Corsa, but I've read that it is loud on supercharged applications as well so it doesn't sound like a good option especially not at twice the price.

Any other ideas?

 

... and get a Corsa. I am most likely the worst about not putting up with exhaust resonance. I had a Airaid intake tube and sold it off due to the noise.
I used to get my hands on Silverado SS mufflers for some added flow without the noise then I went to the Dealership for an oil change and seen they had a new ECSB truck on the floor dressed up with large rims and a Corsa exhaust system. I got a demo ride and even though it was a Sport edition it was tolerable in the cab. Very tolerable. It was a dual rear exit system. Outside it was too raspy for me, then they let me ride in a single side exit Sport edition. Much better sound outside and a tad better inside
I now have the Touring single side and it is really nice. The sound when it opens up is awesome.



I know, it's high dollar. You get what you pay for and that is a straight through high flowing design without the noise inside. If you are going to keep the vehicle for a few years or save your OE pipes incase of a trade it is worth it.
The only time you hear it in the cab is when it is laboring a bit and then it is not really resonance.

Corsa For Hummers

 

There is a reason I went with a single 3" input, but dual 2.5" outputs on my second muffler (the 22" can). Rather than running two 2.5" tailpipes like one would think, I will be narrowing down and running two 2.25" tailpipes out the passenger side, behind the tire. There will be no loss of flow going from a single 3" to dual 2.25" outputs, but there will be a huge loss in overall noise and resonance. Much of the noise we experience is from the 3" pipe from the output of the muffler rearward, which is eliminated with this design.

I've spent over two years figuring out how to get flow without noise, and this is what I've come up with. Everyone I've talked with has nothing but good things to say about my design once they understand it, including people at Magnaflow. I will be sacrificing zero power, as the dual 2.25" out the back give me more than enough flow, but the system will very, very quiet.