Help asap 6.2 l and flowmaster 40 too much drone

[cbprov]

i was reading alot of threads and everyone has a differant answers ,i decided on a flowmaster 40 and removed downstream flapper as was suggested by another member ,i get alot of drone and can hear when engine cuts down to 4cly ,if i reinstall flapper do u think it will get rid of drone ,leaving on a long trip in 2 days and want this fixed ,thanks any other suggestions

[truck_newbie]

Yes, the flappers will most likely remove the drone. Resonance/drone is complicated because there is a lot of physics involved which is why some get the drone and some don't with just a muffler replacement. Without going the j-pipe route to cancel out this resonance, putting the flappers back is your only option. I went through a similar ordeal. See the thread below. 

 

[cbprov]

thanks just read ur thread ,back to shop tommorow ,will post results

[brianc636]

This is reason why a good engineered cat back is solid investment.

[KARNUT]

I left the flapper in and eliminated the V-4 with a tune added performance muffler no drone. You can go with the range also. No need for an expensive full exhaust.


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[OnTheReel]

1 hour ago, brianc636 said:

This is reason why a good engineered cat back is solid investment.

Absolutely. You lose the restrictive flapper valves and get no drone in return.

9 minutes ago, KARNUT said:

I left the flapper in and eliminated the V-4 with a tune added performance muffler no drone. You can go with the range also. No need for an expensive full exhaust.


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Range doesn’t disable DFM. Nothing does.

[KARNUT]

Range doesn’t disable DFM. Nothing does.

Their working on it


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[OnTheReel]

They have said that for a year. It’s just not happening. They even removed the “coming soon for DFM” notes in the compatibility listing.

[brianc636]

I left the flapper in and eliminated the V-4 with a tune added performance muffler no drone. You can go with the range also. No need for an expensive full exhaust.


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If you did this on a T1 with the L84/L87, I would like to know how since no one can tune these engine combinations yet.

[KARNUT]

If you did this on a T1 with the L84/L87, I would like to know how since no one can tune these engine combinations yet.

He didn’t write he had a T1. He said when it drops to V-4.


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[OnTheReel]

Guess I just assumed we are talking DFM since it was posted in the T1/ 2019+ forum, and all 2019 6.2s have DFM.

 

Not meaning to insult the OP, or anyone else but a lot of people don’t really know how the new cylinder deactivation works on the new trucks so they just call it V4 when it drops cylinders. Old habits I guess...

[cbprov]

It is a 2019 sierra at4 with 6.2l thanks 

Edited September 9, 2019 by cbprov

[brianc636]

The muffler for that truck is a 3.5” inlet/outlet. At least on the GMPP exhaust.

I swapped the GMPP muffler out for a dynomax 17517 and a short section of 3.5” stainless tube for a bolt in installation.

No drone and is a nice improvement over the factory unit.

[cbprov]

U left in both flappers

[newdude]

"flowmaster 40"

 

That's probably 99% of the issue right there.  Small body, obnoxious muffler.