Flowmaster

Song · November 25, 2007

FISRT OFF... I AM STUPID ON THIS so I am asking to learn.

I am wanting to put a flowmaster muffler on my 07 NBS. I'm the type that does not like to change the original piping under the truck, just cut the old one out and place the new one in. I've done this on my prior GMC/Chevy's and have been very pleased with the sound.

On this truck I want to do the same but I want to do it myself instead of taking to a shop like before. I have all the tools and lift to do it myself this time.

My question is what inlet and outlet size are these new trucks and it is right, left or center inlet/outlet on the muffler itself?

I have the 4.8L V8. I'm stupid at this point since this will be my first muffler to do.

One more question? Would a flowmaster make my truck sound like a weed eater on the 4.8L?

Nytemare · November 25, 2007

I have an 03 with the 4.8...It sounds just like a 5.3, nice rumble at idle and cruise, loud when I'm on the gas.

A V8 is a V8...it will sound like one. The 6.0 will sound a lot louder, but you'll still get a nice rumble

The stock piping is 2.75". Get a muffler with 3" in and 3" out. Buy 2X 3"-2.75" adapters and your golden.

I have the super 44 on my truck...its a super 40 in a 4" can.

http://www.flowmastermufflers.com/44_super.html

You'll want to get the design that closely matches the stock pipe routing.

I have Duals so I chose 9430452

Midwestcruiser · November 25, 2007

Song, on my last vehicle, an '02 Tahoe, I had the Flowmaster catback system, 3" overall diameter. It sounded great and I'm sure I had some performance gains. I don't think I'll go all out on this truck exhaust-wise but I am considering changing out the muffler to get a more agressive sound and maybe a chrome tip for looks.

Nytemare, how long have you had that 44 on your truck? According to Flowmaster's site, that's the loudest, throatiest sob you can get. How loud is it? Even though it's not touted as a truck muffler, are you happy with it and would you recommend it?

Nytemare · November 26, 2007

I am totally happy with it. Ive had it for 2 months now...it just got broken in, and with the nice cold mornings (32* or so) its pretty loud at startup. I get people commenting on it all the time, it has a really nice mellow rumble at idle.

Its very similar to a super 40 for loudness...but since its a bigger case its a bit deeper. I have 2.5" outlet pipes exiting either side, with a 2.75" single outlet it should be even louder. Its not true dual, glasspack loud, but you know its there.

It makes some popping/crackling sounds when you do a park/neutral rev, but it never pops while driving. It does however Bark loudly when your on the gas...it gets everyones attention, especially the stupid SOB that just cut you off, when you pull around him and give it gas right by his side window.

It also doesn't give a lot of cab drone, only around 35mph or 55-60 mph just as you changed into the higher gear and you haven't backed off the gas yet, probably around 2200 RPM for me, I have 3.42 gears and I do highway speeds at about 1800-2000rpm max.

I would definitely recommend this muffler. Its pretty cheap to boot.

2000DV4.8 · November 26, 2007

I love the way the Flowmaster sounds on my 4.8L. As for the inlet/outlet location, just look at your stock muffler, and see what it is.

Nytemare · November 27, 2007

I love the way the Flowmaster sounds on my 4.8L. As for the inlet/outlet location, just look at your stock muffler, and see what it is.

I love the way seafoam does that...LOL

ws6_guy · November 27, 2007

Super 44 is probably the best they have built, but I dont think its the loudest, the 10 series has the win there IMO

I was thinking of going with those, but true dualed would be way too loud. I have Super 44s waiting to be installed if I could only come up with another $100

As for your project doing it yourself, you will ofcoarse need a little extra piping cause OEM mufflers are always way larger than aftermarkets. Sock is like 24" & the Flowmaster is 13". Also does your tip have a resonator thing after the muffler? That may quiet it down if thats a resonator. idk about NBS exhausts though

davidhughrose · November 27, 2007

How has fuel mileage, particularly highway mileage, been affected?

Nytemare · November 27, 2007

I haven't noticed any difference in fuel millage. Well, after the first few weeks of having it on I haven't noticed much of a difference....the first while I was losing about 150Km per tank, but thats because I always had my foot in it.

Midwestcruiser · January 28, 2008

Should've asked this back in November...on my '05 Silverado 5.3L, what is the stock exhaust pipe size? I want to switch out the stock muffler with a Flowmaster. Thanks.

2000DV4.8 · January 28, 2008

Should've asked this back in November...on my '05 Silverado 5.3L, what is the stock exhaust pipe size? I want to switch out the stock muffler with a Flowmaster. Thanks.

I'm pretty sure it's 3", but not positive. Best way to find out is go out and measure.

todoubled05 · January 29, 2008

good choice on the flowmaster. if I read this right all u want to do replace the muffler? seems posible I would imagin all u would need to do is just cut the old out, mount the new and get a cupling from 3" to 2.75" ( 3" for flow muffler, 2.75 stock pipe) then weld. u might be able to pull off just welding a small piece of piping between the muffler and exit pipe. the flowmaster 40 series is about a quarter of the size of the gmt900 muffler so u will prolly need a foot or two of pipe. as for the sound of a 40 sires on a 4.8, not to worry! I got a single in dual out flowmaster 40 on my 07 4.9 and I was surprised how loud/good it sounded.well worth the 275$ couldent be happier.

todoubled05 · January 29, 2008

deleted due to double post.....sorry

Stros06 · January 29, 2008

Should've asked this back in November...on my '05 Silverado 5.3L, what is the stock exhaust pipe size? I want to switch out the stock muffler with a Flowmaster. Thanks.

I'm not sure about the pipe diameter for an 05, but the 50 series big block muffler would be your best choice if you are looking for a similar muffler size replacement. I had one on a 99 Sierra Classic and loved it. No drone whatsoever, just a low rumble at cruise speeds. That is my next purchase for my 07.

Good luck on whatever you get.