Ideas how to quiet my cabin drone noise please

[Johnunger1]

Hey all. I am looking for some ideas . The drove noise at low rpms is killing me. I has some turbo mufflers installed and that helped but its still so loud. Outside it sounds nice and quiet. What have yall done on the inside to quiet down your rides? Thanks
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[mongocanfly]

Do the pipes run out the back?

[Johnunger1]

Originally Posted by mongocanfly

Do the pipes run out the back?

They turn down just in front of the rear axle
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[MiraclePieCo]

I've had two trucks with exhaust turndowns in front of the rear axle that both had severe drones. Maybe that's a coincidence or maybe it's a recipe for vibration and noise.

[Dan in Pasadena]

Also, move your mufflers as for back as you can. Don’t have them right under the cab floor.

[DPete]

That's how mine are, I can live with the exhaust noise but I get wind noise about 60 I'd like to get rid of, have new door seals, probably not air tight when new and I'm used to todays pickups.

[Dan in Pasadena]

Originally Posted by DPete

....probably not air tight when new and I'm used to todays pickups.

If that’s the standard by which you will judge your Task Force truck... MEH...chances are you will be forever unhappy.

[Greenlee]

Originally Posted by Dan in Pasadena

Also, move your mufflers as for back as you can. Don’t have them right under the cab floor.

I think this is the answer. My exhaust turns down before the rear axle and I don’t have any drone. The mufflers are under the bed not far before the exhaust turns down.

[bosco]

Originally Posted by Dan in Pasadena

Also, move your mufflers as for back as you can. Don’t have them right under the cab floor.

Agree. I moved mine back as far as possible. Also, installed sound matting in the cab. Reduced the drone considerably when cruising on the highway.

[joedoh]

the muffler shop told me that long stretches of tube were what caused the drone, either long pipes to the muffler or long pipes after the muffler. I had a bad drone on a truck with a muffler right before the tip and he put in a small center resonator right in the middle of the long pipe, I didnt lose any exhaust sound but the drone was gone. years later I had a truck with mufflers under the cab and long pipes out the back, it droned enough to make you contemplate driving off a cliff to end it, I replaced the mufflers under the cab with cherry bombs and moved the mufflers back to almost the axle, the drone was gone.

It makes sense on paper, the principle is called standing waves in tubes. take a length of a 2" diameter hose and swing it in a circle, at a certain speed it will howl, and howl at a higher pitch (harmonics) at twice/three/four times the original speed. even if you move your hand so that less of the hose is spinning, the frequency of the howl remains the same because the length of the hose is what causes the standing wave, air bouncing between the ends makes a long standing wave. the way to eliminate the howl is to shorten the hose, so that it takes a lot more energy to spin the hose fast enough and produces a howl at a shorter standing wave (higher frequency). notice that the hose is still 2" in diameter so you havent limited the throughput, just raised the frequency of the standing wave.

[vintovka]

Have same sound but only in OD. 36" real (1969) cherry bombs that point down before rear axle. No problem in other gears. Not real bad but can really tell when the 700r4 goes into od at 45. No need for a tach. Heard this is a very common issue but wondering if i added short angled extensions to direct exhaust back if it would affect performance. Have lots of room underneath and about 10" to rear axle. Would go out under original boards but the power boards are in the way.

[1project2many]

I agree with the folks that are suggesting changes to muffler and tailpipe configuration, although I believe you might have to use trial and error to find the best answer.

I tried positioning the mufflers (Edelbrock turbo style) under the rear of the cab then running short turndowns right off the muffler. Bad idea... resonance at idle was unbearable. I added an H pipe just behind the transmission, moved the exhaust exits to about 4" before the rear axle, and decreased the size of the pipe by 1/4", and the resonance went away.

[vintovka]

Originally Posted by 1project2many

I agree with the folks that are suggesting changes to muffler and tailpipe configuration, although I believe you might have to use trial and error to find the best answer.

I tried positioning the mufflers (Edelbrock turbo style) under the rear of the cab then running short turndowns right off the muffler. Bad idea... resonance at idle was unbearable. I added an H pipe just behind the transmission, moved the exhaust exits to about 4" before the rear axle, and decreased the size of the pipe by 1/4", and the resonance went away.

My glaspacks are as far back as they can go and have the turn downs right at their ends. Cab is fully sound deadened with the thick stick on liner. Will just temporaily attach some entensions to see if i can keep the sound from bouncing back at the cab. May eventually lose the pacs for real magniflows.

[Divine 59]

Have the muffler shop install a resonance tube. Cant post links here but you can search the web for solutions. There is a formula to assist in determining the length of pipe to eliminate the drone.

[vintovka]

Originally Posted by Divine 59

Have the muffler shop install a resonance tube. Cant post links here but you can search the web for solutions. There is a formula to assist in determining the length of pipe to eliminate the drone.

Could a resonance tube be welded in before a muffler?

[1project2many]

Resonators are sometimes very similar to glasspacks in construction. But the length of the resonator tunes it to the frequency of the sound that needs to be quieted. They typically affect a small portion of the exhaust sound.

Originally Posted by vintovka

Could a resonance tube be welded in before a muffler?

Yes. OEM systems sometimes come through with the resonator first.


A balance tube will reduce the pressure of the pulses through the muffler. This will decrease the volume level. It also connects both pipes which doubles the frequency of the pulses through the tailpipes.

[Patrat]

resonators definitely work to reduce drone and overall volume of sound

[mr48chev]

Had a buddy with a car with turbos with the turn downs in front of the axle that I quit riding in because the drone on the highway gave me a severe headache. That was the worst one for it I ever rode in or drove though.

It would help to run some pipes out in front of the rear tires to get the concussion from the exhaust out from under the truck. You will still get some drone but it will be a lot less. Srill nothing matches exhaust pipes that run clear to the back bumper either exiting straight back or to the sides. Sometimes gas tanks and everyting else don't allow for it on these trucks but it makes a serous amount of different for long road trips that last several days and cover several thousand miles.

[jweb]

When I first put my truck together I did my own exhaust. It had turbo mufflers under the cab and turn downs just before the axle. It was loud and had terrible drone.

When I finished my rear suspension I took it to an exhaust shop that has been around forever. I asked for the mufflers to be further back and the pipes to exit the rear to quiet it down. The owner of the shop explained to me that the further back the mufflers the more drone you would get. Basically the sooner the exhaust was muffled the better.

I am no expert so I don't know if this is a fact, but I do know my exhaust is almost too quiet. Even my wife wishes it was a little louder. I have an LS1 wilt headers, H pipe, Magnaflow mufflers and my exhaust turn downs are just behind the rear bumper.

Wind noise and a few rattling noises are still a problem

[b-mac]

After reading all of this, I think I just saved myself hundreds on all the new doors and window seals.

It's going to be loud anyway. Drive the balls off of it...keep it off the highway.

[dsraven]

I'm betting the H pipe is a helper for drone as well.
I had a guy ask me to about his catalytic converter on an astro van. he had it removed one week, the next week he asked me to put it back on. the drone in the bread box was out too much. the converter was installed soon after the Y pipe with a single pipe from there back.
personally, I wanna hear the music or conversation in the cab plus be able to hear the grand kids later. not a fan of loud interior noise. to each their own though. it is a fact that loud noise causes hearing loss.

[mikebte]

Originally Posted by dsraven

I'm betting the H pipe is a helper for drone as well.
I had a guy ask me to about his catalytic converter on an astro van. he had it removed one week, the next week he asked me to put it back on. the drone in the bread box was out too much. the converter was installed soon after the Y pipe with a single pipe from there back.
personally, I wanna hear the music or conversation in the cab plus be able to hear the grand kids later. not a fan of loud interior noise. to each their own though. it is a fact that loud noise causes hearing loss.

I can agree, cats do aid in the noise. They are just an additional buffer in the pipping. I have duel cats on my 59 and its not bad. Not yet at least.

[1project2many]

personally, I wanna hear the music or conversation in the cab plus be able to hear the grand kids later. not a fan of loud interior noise. to each their own though. it is a fact that loud noise causes hearing loss.

My truck is quiet enough to have a conversation in as long as the windows are up. I'm starting to hear wind noise around the LH door which tells me it might be time to replace door seals. The cab is so airtight that I have to open my window slightly so passengers can close the doors from inside. I'm not bragging... it was pure luck that it came out like that. But I am saying it's possible.

I have tinnitus pretty badly. I'm sure the years around the open header cars at the track did plenty of damage. Then the years of driving a convertible with all that wind noise didn't help. Of course I used to drive my unrestored TF all over at 70+ mph with the wind screaming through the cab as well. I had all the reason in the world to think it didn't matter.

I've played the sound I hear for other people and it's so loud they look like they're in physical pain. There are times after I get home from work when I won't let my kids talk to me because the noise and pressure is so bad. In the winter when the shop truck has agressive winter tires on I actually wear earmuffs while driving trying to keep my ears from going crazy. There is no such thing as silence for me anymore.

Please, do the work to quiet the interior of your trucks.

[Black_Sheep]

Originally Posted by 1project2many

I have tinnitus pretty badly. I'm sure the years around the open header cars at the track did plenty of damage.

Me too, 30 years working in a truck shop, loud cars, gunfire, etc... For me it's like a million crickets chirping, 24/7.

I had dumps right off the mufflers for one summer, the drone at certain speeds was so annoying. I stopped at the Flowmaster booth at Back to the 50's, their recommendation was full exhaust. It seems a lot better, although I put a lot of effort into cab sound deadening too. It was time and money well spent...

[vintovka]

Have tinnitus pretty bad as well ( F-111a jet engines and 18 (?), 500 bombs going off nearby) The VA recently provided me with tinnitus suppression, Oticon mini hearing aids amd they really work. Also work with phone and tv. I did not realize how bad my hearing was until i got them. -Even engines and key in igniton car chimes sounds entirely different