Muffler Replacement

**thejms** · 02-09-2009, 11:16 PM

So I have a friend with a 03 Sierra and he has a flowmaster Super 40 single in/dual out muffler, he is giving me a heck of a deal on it.

I went down to a local muffler shop and got their opinion and they told me that I needed a dual in/single out if I wanted to just swap out the stock muffler.

I realize that just replacing the stock muffler doesnt improve the performance as much as mandrel bent tubing and a full cat back system, but at my current budget this may just have to do.

Is what the guy telling me on que or is he just trying to make me buy the muffler there?

**mjalstad** · 02-09-2009, 11:48 PM

Yup, I believe he's right

**chevyrulz** · 02-11-2009, 12:05 PM

gm stock setup usually has true duals to the muffler then 1 pipe out the back. look under your truck. if there's 2 pipes going from the muffler to the engine then you will need a y pipe welded in to make that single in dual out muffler work. the y pipe is a 2 into 1 adapter. your best bet is to find either a dual in muffler or go with 2 single in mufflers. i've got a dual in dual out 2.5" flowmaster 40 on my tahoe. picked it up for $120 and then welded on some turn downs and clamped it to my factory set up after i sawzall'd everything of from the cat back except about 1 foot of each pipe. the sum bitch is loud thats for sure. this setup replaced my glasspacks. i got 2 glasspacks off ebay for like $40 bucks. the glass packs actually resonated much less in the cab and were louder @ full throttle. i think the resonation is more because the glass pack setup was exiting by the rear bumper and the flowmaster i got is exiting right under the rear seat. the flowmaster 40 makes it sound like i'm driving a drag racing car which means you can really hear me coming. both sound great, flowmaster sounds fast and glasspack sounds loud. the glass packs were Flowtech Red Hots if i remember correctly. super cheap on ebay!

edit:

also, the stock pipe on my tahoe was NOT 2.5" so i should have measured 1st. i had to weld on reducers to get it to clamp on to the factory pipes. i would have welded to the factory pipes but they were mad rusty since my tahoe is a 1997 from south florida

**thejms** · 02-11-2009, 08:14 PM

Originally Posted by chevyrulz

gm stock setup usually has true duals to the muffler then 1 pipe out the back. look under your truck. if there's 2 pipes going from the muffler to the engine then you will need a y pipe welded in to make that single in dual out muffler work. the y pipe is a 2 into 1 adapter. your best bet is to find either a dual in muffler or go with 2 single in mufflers. i've got a dual in dual out 2.5" flowmaster 40 on my tahoe. picked it up for $120 and then welded on some turn downs and clamped it to my factory set up after i sawzall'd everything of from the cat back except about 1 foot of each pipe. the sum bitch is loud thats for sure. this setup replaced my glasspacks. i got 2 glasspacks off ebay for like $40 bucks. the glass packs actually resonated much less in the cab and were louder @ full throttle. i think the resonation is more because the glass pack setup was exiting by the rear bumper and the flowmaster i got is exiting right under the rear seat. the flowmaster 40 makes it sound like i'm driving a drag racing car which means you can really hear me coming. both sound great, flowmaster sounds fast and glasspack sounds loud. the glass packs were Flowtech Red Hots if i remember correctly. super cheap on ebay!

edit:

also, the stock pipe on my tahoe was NOT 2.5" so i should have measured 1st. i had to weld on reducers to get it to clamp on to the factory pipes. i would have welded to the factory pipes but they were mad rusty since my tahoe is a 1997 from south florida

Thanks for the advice!

Ya I dont know where my head was at the time, I just peaked under and basically confirmed everything you said. It is a true dual into a single muffler. I think I am going to go with a dual in single out 50 HD Seriers flowmaster. Just gotta save up the money now LOL.

**chevyrulz** · 02-16-2009, 11:54 AM

Originally Posted by thejms

Thanks for the advice!

Ya I dont know where my head was at the time, I just peaked under and basically confirmed everything you said. It is a true dual into a single muffler. I think I am going to go with a dual in single out 50 HD Seriers flowmaster. Just gotta save up the money now LOL.

yea the 50 series won't be near as loud as the 40 series. personally i prefer no cat or muffler myself...thank God we don't have vehicle inspection here in south carolina