I have a 2001 GMC 2500 HD with a 8.1 496 and use this truck to tow a 35' 5th wheel camper. Long story short it needed an exhaust system (muffler rotted) so I ordered a Dynomax "Ultra Flo" stainless catback system from Summit. To my surprise the system lined up and fit! Has huge 4 inch stainless pipe with a 5 inch polished tip. Now for the bad part... you can no longer drive the truck! The exhaust noise inside the cab is unbearable when under a load, worse with windows up, radio useless. I plan on calling Dynomax Monday to see what can be done but i'm looking for ideas incase they tell me "that's how is is".
CK5
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New exhaust now killer exhaust drone!
- Thread starter GMC Truck
- Start date
What's the point of that big of pipe on a gasser? I would guess that's part of it..
y5mgisi
1 ton status
My guess is exhaust wrap, resonator, and possibly "heat shields". That is, if you want to keep this exhaust.
wheeler
1/2 ton status
i would second the larger piping, causing some of the drone. also if its thinner steel than stock, or it could be the muffler.
We had an '00 C2500 with a vortec 454 and it had a nice dual exhuast system with two mufflers side by side and the drone was absolutely horrible. I got "used" to it and made multiple trips from Cali to Texas and back in that truck but it always bugged me.
How far is the tip where it dumps from the muffler?
How far is the tip where it dumps from the muffler?
The exhaust tip is in the factory location. Single exhaust with tip on pass. side rear corner of bed. The pipes are really not that much bigger than stock. 4 inches vs 3 1/2 inches and bent almost exactly as the original. My guess would be the muffler. Dynomax has a "Safe N Sound" warranty and according to Summit they will make it right with me. We'll find out on Monday cause they are gonna hear about it. (no pun intended)
I tried this system on my '03 2500HD with the 6.0L (basically the exact same system...muffler, 4" tailpipe, 5" tip). Drone was horrible on it and I couldn't stand driving it. Had bought the system at the Jeg's retail store (lived closed to it) and had no problems taking it back. Removing the 5" tip did seem to help but not enough.
you ask me dynomax is cheep these days .
muffler placement alone is 1/2 the battle . do what ever you can to keep the muffler away from under the cabin floor. ( found this out first hand ) my old crew cab 2wd moved it back just under the box and not cab floor and WOW so much better.
also tail pipes out the back/side to not let the exhaust echo under the body . ( found this out first hand ) my old plow truck I finaly added a tail pipe to back bumper and 500% less in the cab drone noise.
and if flowmaster biggest body case / highest # option like 70 series / and delta flow option also helps . ( found this out first hand ) the low # 40 super 44 are worst for long drives.
I just put a kit on for a guys 2012 challenger hemi . flowmaster cat/back American thunder = 40's for mufflers. oh my god the drone was ungodly inside after. cause the new kit places the mufflers under the floor pans of the back seats. original placement is directly in the back under the trunk @ bumper.
I don't know how the guy could stand it but he loved it .
hope my info helps and as said most of it was first hand learned my self the hard way .
muffler placement alone is 1/2 the battle . do what ever you can to keep the muffler away from under the cabin floor. ( found this out first hand ) my old crew cab 2wd moved it back just under the box and not cab floor and WOW so much better.
also tail pipes out the back/side to not let the exhaust echo under the body . ( found this out first hand ) my old plow truck I finaly added a tail pipe to back bumper and 500% less in the cab drone noise.
and if flowmaster biggest body case / highest # option like 70 series / and delta flow option also helps . ( found this out first hand ) the low # 40 super 44 are worst for long drives.
I just put a kit on for a guys 2012 challenger hemi . flowmaster cat/back American thunder = 40's for mufflers. oh my god the drone was ungodly inside after. cause the new kit places the mufflers under the floor pans of the back seats. original placement is directly in the back under the trunk @ bumper.
I don't know how the guy could stand it but he loved it .
hope my info helps and as said most of it was first hand learned my self the hard way .
CGT80
1/2 ton status
I run a 406 sbc and 3" single pipe and high flow cat. I have had the original 40 series flowmaster, the 50 series, and now the super 44. The 40 was loud and maybe a tad crackly. I later cut the tail pipe off after the muffler, and the drone was awful. I think I started with the 50, but I hated the sport truck sound.
The super 44 is very deep and has a lot less drone than the 40, but it is loud and has drone when towing my 8-9k pound toy hauler. I am going to try dynomatting my floor and dynomat floor insulation on top of that with carpet on that, vs the lmc insulation and carpet that is there now.
My k5 has a tbi 350 and a flowmaster 70 series. It is perfect, but I do miss the muscle car sound of my pickup, especially since it has been down for a few months. I wonder how the 70 would sound on a built engine like the 406 or a big block like the OP's truck.
I would say to check muffler placement and either change the muffler or add a resonator.
The super 44 is very deep and has a lot less drone than the 40, but it is loud and has drone when towing my 8-9k pound toy hauler. I am going to try dynomatting my floor and dynomat floor insulation on top of that with carpet on that, vs the lmc insulation and carpet that is there now.
My k5 has a tbi 350 and a flowmaster 70 series. It is perfect, but I do miss the muscle car sound of my pickup, especially since it has been down for a few months. I wonder how the 70 would sound on a built engine like the 406 or a big block like the OP's truck.
I would say to check muffler placement and either change the muffler or add a resonator.
I know if you run downspouts instead of tailpipes you get a loud drone,even on a stock muffler ,single exhaust...my old 235 straight six in my 56 Chevy truck droned like a turbo-prop plane when you lugged it down...and it had a round stock muffler and downspout..
I have thrush glass packs on my 6.2 in the 82 K2500 and surprisingly they dont drone,they have that "fraaaap" sound like a small block,and it has only downspouts too..guess diesels are different..
Worst truck for exhaust droning I had was my 72 K5 when I first got it...someone put those corvette side pipes on it ,that thing gave me a headache in 5 minutes!..I was kind of glad when they rotted out and had to be replaced..it was like driving a caddy after I put dual stock mufflers back on it..actually could hear the radio again!..
I have thrush glass packs on my 6.2 in the 82 K2500 and surprisingly they dont drone,they have that "fraaaap" sound like a small block,and it has only downspouts too..guess diesels are different..
Worst truck for exhaust droning I had was my 72 K5 when I first got it...someone put those corvette side pipes on it ,that thing gave me a headache in 5 minutes!..I was kind of glad when they rotted out and had to be replaced..it was like driving a caddy after I put dual stock mufflers back on it..actually could hear the radio again!..
I finally got tired of drone in the general, moderately cam'd 350, and put an 18" Magnaflow in. Much happier. Sounds good in the crew cab now too with TBI350 no cat.
I have the same stainless kit on my hd, I also have shorty jba headers. I really can complain at all, sounds good and its not too loud but that's on a 6.0 truck. Its on for a few years and still is in good shape. About 10 years ago when I first bought the truck I put on a flowmaster kit, I hated the drone...I pulled up the carpet and pulled out the seats, I used dynamat on the whole floor area..maybe that's why mines not that bad. The flowmaster kit only lasted 3 years then they warrantied it. after it was warrantied it lasted another 4. It was a rotted mess but sounded good.
Also on that note... I have a friend with a 2012 1500 sierra, he put on the mbrp kit and hated the drone. He swapped the muffler to a magnaflow and has been fine ever since.
Also on that note... I have a friend with a 2012 1500 sierra, he put on the mbrp kit and hated the drone. He swapped the muffler to a magnaflow and has been fine ever since.
Well i'm calling Dynomax on Monday to see what can be done. I also think the muffler is the offending part but my options are limited by the size of the pipes, not too many choices for 4" inlet and outlet that are straight inline. Just driving around it's not real bad but it not something you want on a truck that is going to pull a 8000 lb camper 2 or 3 thousand miles.
I had dual flowmaster knockoffs on my 00 GMC and it would rattle the back of the cab because of the drone (still had the converters on it then). Now it's got 3" single with a hooker aero chamber and no cats, the drone is gone now.
How about visiting a similar Thread on this link with this Title ["Q for Mufflers' Experts for my 8.1 (How to reduce sound resonance?")].
Hope this helps. As for my post-experience, the sound improved alot, but 'some acceptable drone' still exist - and I may consider fitting in a 'resonator'!
Funny how we all seem to have the same issue, we all want better performance with an exhaust system and then hate the system. I wanted something like stock that flows better to help with power and then hate the noise. The system I bought looks great and fits great but it took a regular driver and made it so you would not want to drive it... go figure!
Dynomax does make a bigger version of that muffler that may help, but the muffler that comes in the kit is already pretty big. After removing the catback kit I tried a pair of the VT mufflers and just spliced them into the stock pipes (dual pipes to dual 3" mufflers then Y's to a single 3.5" tailpipe). On paper the VT's looked good as they were supposed to be mellow while cruising but "open up" during heavy throttle for a good sound. The first set rattled so bad people would stop and look at me when I drove through town, so took them off and got a second pair after Dynomax tech said they had some issues on earlier ones. The second pair was exactly the same. I then traded them in on a pair of 14" Ultraflos. Actually pretty happy with the way they sounded and barely noticeable in the cab while on the freeway. The only trouble was these stainless steel lifetime warranty mufflers lasted less then 3 years. Currently have a set of 18" Magnoflows (again, just spliced into the stock pipes) and honestly don't like them as much and they have more interior resonance/drone.
Looking online there is limited choices for mufflers that will fit the large 4" pipes. If all don't go well with Dynimax tomorrow I may get a Flowmaster big block series and weld adaptors to it to fit just to try something different.
you should never choke down exhaust flow then bump it back up to fit the tail pipe.
True
......but this is what life is about....try & satisfy. Having said so; I still have some space to trade off 'little sound fun' for sake of people's privacy in town and for my own peace of mind!While on the subject; I read about the "Hooker Aero Chamber Mufflers" and they seem to be 'potential', but I noted that the Hooker Muffler's total length is (18 in) compared to the Flowmaster Big-Block 70-Series (28 in) - which am currently using on my Sierra 8.1 (still with some drone).
I don't think the loss of '10 in' of muffler won't impact the sound! So, I will stick to the Flow's with going along with Dorian's advice (i.e. to fit the Cat's back into the Pipes); which am positive will cure the drone! This will be my plan forward.
