Rev matching 2017 Sierra 5.8 after muffler install

[FIREBLADE74]

I just installed a magnaflow muffler 12198, sounds good. Truck has more pep now. 

 

I dont know if my truck alwys did this but it is very noticeable now when coming to a stop as it goes through the gears. Is this normal?

 

also the rpms seem to hang when slow maneuvering like in parking lots. 

 

I hope im not messing anything up. 

[Sierra706]

Normal. You just didn’t notice it before


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[cbrsilv15]

If you just installed a muffler and that’s all, then it’s normal like posted above. A muffler swap will literally just give you a different tone. 

[FIREBLADE74]

THats what I thought!! It’s kinda cool almost like my G35. 

 

 

 

Thanks guys

[FIREBLADE74]

Oh I removed Eve from the muffler back and installed muffler turned down before rear axle

[Krusty]

Best mod U can make - especially for the 6.2l boys.........

[FIREBLADE74]

Upon further inspection of the welding, the dude was apparently taught by Stevie Wonder. His work is horrible!!! Exhaust leaks from not welding the top portion of the pipe, crooked turn downs. I’m going to have to get this redone. Only good:

 

He didn’t butcher my flapper. 

Only cost $40, u get what u pay for. 

The sound, sounds like the 4 horsemen coming.  

Went from 9mpg in town to 13mpg. 

[cbrsilv15]

There's something besides the muffler that yields 4 mpg extra.... The muffler is just a tone change.

[Logan Lanfear]

4 minutes ago, cbrsilv15 said:

There's something besides the muffler that yields 4 mpg extra.... The muffler is just a tone change.

Yeah, just that muffler isnt changing the flow of the exhaust all that much.  There's resonators and cats still in the system on top of a small factory tube size.  

[FIREBLADE74]

Ijs, since the change I’ve seen that increase. Maybe unrelated but it looks good 

[HeySkippyDog]

Leaking welds?! Lol. How did you not check before you left?

[FIREBLADE74]

I did but was so pissed at the work I refused to let him go back under my truck. Lol. 

[Krusty]

It always amazes me how the competent shops can weld all the way around - when you can't really see the top.....

 

[FIREBLADE74]

Ok got my exhaust welded correctly great work looks factory but they had to remove the flapper valve. 

 

It sounds horrible when v4 kicks in. Is it possible to purchase a new one from the dealer? The shop said hey wouldn’t charge me to weld it back in. Also I’m running dual turn downs before the axle. 

 

Btw the first muffler shop used jb weld to close up the gaps smfh!!

[HeySkippyDog]

Dude...

 

If all you had changed was a muffler and the exit pipe, there was no need to remove the flapper.

 

You can order another one, don't expect it to be cheap though.