Sound Deadening and Engine Noise

[Gumby83]

Hey fellas, I have a project i've recently got on the road. Everything is great except the cab noise.

I sound deadened the hell out of the cab. Killmat on the floor/firewall with Siless foam ontop before jute carpet. It does make the cab much more quiet, but i got a serious resonance/drone around 2400rpm.

Going to rebuild the exhaust to try to isolate it but i want to know if there are any tips/tricks you guys might have to quiet the cab down.

Some facts about my truck are the truck was extremely rough when i got it, holes in the floors, rotted out cab corners etc. also doors don't close nice, they are abit out of alignment. The roof does not have sound deadening material. The engine is a built 370ci Turbo LS, i have a 4 inch downpipe that runs right next to the passenger firewall that has to stay. Any advice, would be much appreciated.

[LS short box]

And the 4" down pipe goes where? All the way to the bumper? No muffler?

[SkinnyG]

Any exhaust that exits under the truck is going to drone.

These trucks are also just plain noisy. They are a tractor, with a cab.

I'd love to see your truck in person though!

[Gumby83]

Originally Posted by LS short box

And the 4" down pipe goes where? All the way to the bumper? No muffler?

4 inch downpipe, to 4 inch to dusl 3 inch splitter. dual spintech 6000 mufflers, then through the trailing arm crossmember, turn and bend inder the frame to just below the passenger stepside step. then a 12 inch resonator on each.

[Gumby83]

Originally Posted by SkinnyG

Any exhaust that exits under the truck is going to drone.

These trucks are also just plain noisy. They are a tractor, with a cab.

I'd love to see your truck in person though!

its a side exit under the stepside step on the passenger side. I kinds figured they are old trucks, and not going to be super quiet, but i think there is room for improvement lol, already added 1000lbs to the weight of the truck vs Original weight. a bit more sound deadening cant hurt anymore.

Its a love or hate thing i find, some dont like my solutions to problems, but i wanted a unique daily thats fast and easy to drive. got that, few minor quality of life stuff upgrades tonmake, such as power steering getting a upgrade and noise reduction in the cab. If you spot my truck anywhere come talk, i dig your youtube channel!, my truck is easy to spot due to liberal use of hole saws, sawzalls and a welder. ��

[Wikid61]

Killmat put on the outer door skins. The over head metal. Is the gas tank wrapped in 'mat? Or even the silver bubble wrap from MENARDS? The floor/cab upright behind/under
gas tank covered?

[Grounded63]

The farther you get the mufflers from under the cab. The quieter it will be inside the cab. At least that's been my experience. Kinda goes the same for where the tail pipes exit.

[Gumby83]

Originally Posted by Grounded63

The farther you get the mufflers from under the cab. The quieter it will be inside the cab. At least that's been my experience. Kinda goes the same for where the tail pipes exit.

oooh. this could be big. did not know.that, thank you.

Originally Posted by Wikid61

Killmat put on the outer door skins. The over head metal. Is the gas tank wrapped in 'mat? Or even the silver bubble wrap from MENARDS? The floor/cab upright behind/under
gas tank covered?

All yes,.except for the roof.

[AcampoDave]

I did my hood and got a 4db reduction in the cab. https://67-72chevytrucks.com/vboard/...d.php?t=808418

[rideblue00]

AcampoDave: have any pics on how you laid it out?

[theastronaut]

Resonators after the manifolds/headers to kill drone/harsh tones, and adding an X pipe will also smooth out the tone and make it less harsh in the cab. Vibrant makes really good resonators.


There are a few different "kinds" of sound to deal with in a vehicle and peel and sticky Dynomat type deadener only deals with one kind. Unfortunately the aftermarket pushes it so hard that the other ways are pretty much totally ignored. Sounddeadenershowdown used to be an excellent source of info and products to deal with the full spectrum of noise reduction, they're closed now but you can still access the info on their old site here-

https://web.archive.org/web/20210609...rshowdown.com/

[AcampoDave]

Rideblue: Just the ones in my link on post #9 of this thread.

[corvettejim1968]

Fat Matt rattle trap is what I use for my vehicles. You can buy it on eBay it's thicker and tackier than dynomat making it a better product for less money. In my truck I did inside the dashboard under the rubber floor mat inside the doors behind the seat and under the seat. My truck has zero rattles. The stuff really helps a lot and inside my doors I did multiple layers to really deaden them.

[jweb]

Noise in cab and you already have all the sound deadener, here are few things:

These may seem small but make a really big difference.
1: Eliminate any holes and seal any that have cables or wires coming through, especially on the firewall and floor.
2: Make sure all of your seals are are in good condition and sealing properly.

Drone:
1: The exhaust should exit as far back as possible, past the rear bumper is ideal.
2: Add an X or H pipe, this helps a lot on LS engines.
3: If I remember those spintech mufflers are loud. You could get a quieter muffler and add cut outs for those times you really want to make noise.

[Backpayne]

Just have a j-tube made for your exhaust. I built one for my Ram 1500 and it completely eliminated the drone/resonance from my Flowmaster muffler.

[rideblue00]

Backpayne, whats a J tube?