What is the quietest aftermarket cat back system that will make more power than stock? For a 2003 Avalanche 5.3L

 

i don't know about the quietest system out there but the magnaflow dual in dual out 2.5 inch with the built in X has caught my eye. from reading old post, if you get the 24 inch muffler it will be relatively quiet. it will get a little louder if you go with the 18 inch. also, magnaflow has probably the best rep on this board for making more power.

 

i ordered a magna flow catback for my truck, would'nt fit. they assured me that it was the right one but the hangers were in the wrong place, the bend was wrong. anyway ended up with a dual in single 3 1/2 out flowmaster big block muffer i think they called it. seems to flow better and is very quiet. can't vouch for power increase, but it feels better especially when towing. e p.s i think it's a four chamber, so i'm sure it does'nt flow as well as a straight through magnaflow but i've heard the magnaflow on a 6.o and it was at least four times as loud.

 

I have the Magnaflow Cat-Back on my 2003 Avalanche right now. it is pretty quiet compared to what I am use to. I have to say that it has a pretty agressive tone to it, but never gets obnoxious, even at WOT. I really like it.

 

If you want a little better flow without in cab resonance, here is what I did.
I have a 2003 SS Silverado muffler on my 2003 Z71. It is deadly silent in the cab. You know it's different but not in a resonance manner. It's a little louder outside. What I also like is the amount of increased flow. Corsa flow tested many of GM's OE mufflers. You can call them to confirm, but I believe these are the numbers... SS flows 441 CFM the stock flows 280 CFM, a 161 CFM increase. The SS 6.0 pumps a claimed 345HP and is higher in compression so I believe it is better. My SOP dyno felt a better run out in upper RPM's without loss of low end or MPG. I had a muffler shop cut my OE Y-pipe behind the O2 bungs and run true duals into the SS muffler. The hangars fit like the OE. Because the SS has a squared off rocker panel the muffler tail pipe looks low at some angles and most folks complement me on it. I see some OE pipes hanging allot lower. See a pic here, http://users.adelphia.net/~allen22/1Truckpage_2.htm .
I seen them up for sale on ebay and @ http://www.silveradoss.com.

Gibson advertised "The quietest aftermarket Cat Back available". I had one on my 97 Z71 ECSB 5.7. It was horrid! It resonated in city cruising and the low end power dropped off and MPG went with it. It did make more power in the upper RPM's however.
I tell you, I cannot stand in cab resonance. I wanted the impossible and did not get it with the Gibson. They would not take it back. I ran it a week and dropped it on the ground and practically gave it away.
I'm very close with my SS setup. The best money I've spent on a single mod is on my Nelson 93 Tune.

 

I'm surprised the SS system flowed that well! (That's cool.) Word is, the SS muffler has a 2" diameter tube in the muffler, for ALL of the exhaust gasses to pass through.

I think the questest system could be built out of Magnaflow mufflers... just got for the largest size you can fit!

I had a Borla 2.5" single system on my old 4.3 ZR2 S10. It had a very, VERY mild grumble to it. It was what a stock system should sound like on one of those trucks. I was bummed it was not louder. It was impossible to hear with the windows down, over 25mph or so. There was NO change in interior noise over the stock system. I'm not sure how they sound behind a full 8 cylinders.

 

I've got a Gibson cat back on my truck. It's a little louder than stock, but not much. Could feel a pretty good difference after install.

 

I had a Gibson single-in, single-out, side-swept and like the other poster, it blew. Resonance from 1600-2200 RPM's. Yuck.

Got a Flowmaster 70 series big-block muffler on the advice of 'muffman' at the Chevy AV site with custom dual out pipes in the back. You should check him out at the site: (Muffman @ CAFCNA).

No resonance at all. Throaty sound when accelerating, little to no noise at cruising speed. Closest to stock from what I've heard. But you still know I have a cat-back.

Good luck. Let us know how it goes.

 

I have a 5x11x22 Magnaflow on my F150...it's VERY quiet all around. Freeway cruise, idle, and acceleration.

 

I did the same thing that therock did. I found a take-off 04 SS system at a local muffler shop for free. All I had to do is pay him to modify it to fit. We had to shorten up the pipes a little bit since my truck is a regular cab. We also modified the hangars slightly to bring the tail pipe up closer to the body.