Exhaust and Drone sounds
 

On my 1955 2nd series , I did what I always do, I eliminates extra piping and just turn down right before the axle and let me tell you there is massive drone coming into my cab, is this typical with trucks. Im running two magnaflows that are seated right after the cab , I idle at about 700rpm and the sound vibrates my ears, Im 45 years old and never felt like a old salty dog till now.......crazy to think that Im complaining about a loud truck!
The exhaust system is almost 15 years old and I can hear something going on in the baffles but Im curious if any one here is running a side exit right before the back wheel , that's the setup I want to run and what exhaust everyone is happy with.
Im also buying the Noico brand of sound deadner and doing my cab and hopefully inside of my doors as well ...

Re: Exhaust and Drone sounds
 

The same thing has happened to me. Twice. It happened when I was 18 and tried to build my own exhaust in a 55.2 and it happened with my current truck, a '57. Both trucks had mufflers near the driver's seat and short turn downs. Different mufflers for each truck, different diameter pipes. With the current truck I tried to find other ways to fix the issue before changing tailpipes. I added an H pipe and switched mufflers but it really didn't cure anything. Then I tried replacing short down pipes with longer then longer again. The cure for this truck, a long bed, was to dump the exhaust about 36" from the back of the cab.

Re: Exhaust and Drone sounds
 

I used 2 layers of Dyna-mat. And 2 layers of thick carpet padding through out the entire cab.. Then installed carpet on top of that. Cab is very quite inside. So for me it was worth all of the extra effort.
I am also running 2.5" pipe, block hugger headers and a single 2 in 2 out Borla muffler which is mounted under the bed. My pipes do run straight out the back though. Truck sounds nasty when you stomp it but somewhat tame otherwise.

Some guys say it helps with the drone if you mount the muffler at least 3/4" of the way back to the rear. Also an x pipe or H pipe up front may help.
However; Anytime you exit under the mid section of the vehicle- and don't have much pipe after the muffler You will increase your chances for that annoying Drone.

Re: Exhaust and Drone sounds
 

got a shop vac? take the hose off and swing about 36" of it (just hold the rest) around in a circle. at a certain speed you will hear a clear note coming from the hose. if you spin it faster the note will change in pitch to the next higher octave. if you cut the hose shorter and spin it at the first speed, the note will change to be slightly higher in pitch than the first note.

what you have just done is demonstrate a "standing wave". big diameter tube with long unbroken stretches are lousy with them. what is happening is the air is bouncing back and forth in the tube at a specific frequency known as the resonant frequency. a resonant frequency is when the input power is the least when compared to the output sound, the easiest frequency it can make.

when that resonant frequency is in the 120-300hz range, it makes an awful drone in the cab. I have had it. in my experience putting the mufflers closer to the manifolds helps with drone (shorter stretches of pipe, less length, higher resonant frequency). if your mufflers are at the back, consider adding a mid-pipe silencer, it can be fancy like the center muffler from a cummins dodge truck (what I use) or it can be as simple as the smallest glasspack/cherry bomb they sell (I saw an 8 inch one), it wont cut down the sound you love, it just breaks that long standing wave.

Re: Exhaust and Drone sounds
 

When I first found my truck, it had a HORRIBLE drone. 283 V8 with dual 2 1/4" pipes and old Cherry Bombs that ended under the cab and that was it. The mufflers sounded empty when I tapped on em. First thing I did was add pipes from the mufflers and had em exit out the side just in front of the rear wheels, which helped quite a bit. That was last year.

Since then I've redone the entire system with dual 2" pipe into Porter steel packed mufflers that exit out the sides and it's awesome! Mellow deep tone, sounds great when I step on it...and zero drone.

Re: Exhaust and Drone sounds
 

I had a buddy in the 70's who bought into that turbo muffler with turn downs in front of the axle thing that was the hot lick then on his late 60's Roadrunner and I honestly couldn't stand to ride in it more than across town. I rode 40 miles down to the drags with him one Sunday and was looking for a ride home with someone else as the drone was unbearable.

I'd say Joedoe hit it though in that certain setups are inclined to have that drone that drives you nuts and small seemingly insignificant changes can make a big change.

Or you just entered the world of old uncool dude who no longer can deal with That kind of noise anymore.

Re: Exhaust and Drone sounds
 

Thanks for the replies , I do have full length headers and the mufflers are right between cab and back axle. I started using the 3m sound deadening materials from my father in laws body shop, and Im using that on the back half go cab and roof since it has a nice black finish, and when I get my Noico stuff Im going to cover the floors and firewall with it then do the carpet mat onto of it too.
I do plan on exiting before the rear wheels, and Ive always ran Magnaflows but I have been entertains the borla mufflers. Im used to 60's style muscle cars so Im just amazed at how loud the interior is in these 1955 tin cans!!
if I start wearing crocs I'll be the uncool dude

Re: Exhaust and Drone sounds
 

On a side note i tried every way to stop the drone from pipes downtuned just in front of rear axle. Whenever it dropped into overdrive the drone was very,very bad. Enough to give us migraines. Had exhaust piped back and almost past rear bumper. Drone is GONE and sounds tons better. See pics in Signature link.

Re: Exhaust and Drone sounds
 

Look at the big brain on this guy!

Re: Exhaust and Drone sounds
 

Interesting science JoeDoh

I always like to look at what the GM and Ford Engineers end up with. Both Companies have millions of dollars in R&D budgets to figure this stuff out. No Aftermarket company comes close to what the OEM Engineers can achieve. Take the New Mustang or New Corvette- Both sound Awesome! Stealthy at IDLE. Stomp it and they sing all the right notes. How did they route their exaust? What materials did they use? They are required to do this with Cats and still make it happen!!!

No Drone going on with these.

So I guess based everyone's experience here:

:If you end your exhaust under the vehicle- Expect to have some level of drone.

Re: Exhaust and Drone sounds
 

I have had drone on two trucks with pipes out the back. I have had no drone on trucks with axle dumps. When you add length to pipes (or shorten them) you are inherently changing the resonant frequency. See my comment above on cutting the length of the pipe and its effect on the frequency. I think a straight through muffler acts like a continuous piece of pipe for the standing wave, and a chambered muffler does not, but that is just a theory.

what got me interested in it was hearing a (then) new 350z from just behind and beside it as it ran through the gears, fantastic sound! I started researching the design and found an article discussing how Nissan used Yamaha (the piano division) to find the right placement for silencers and mufflers and tune the sound, even choosing the resonant frequency and related harmonics to compliment the standing wave in the INTAKE. Apparently Lamborghini and Ferrari use the same technologies to tune their sport exhausts. I started learning abbout designing pipe organs of all things, and learned more about standing wave design. it was a rabbit hole for sure.

Re: Exhaust and Drone sounds
 

I ran Magnaflow mufflers just under my cab for a few years and I really don't think it was drone. I think it was just loud having them exit right were you're sitting.

I had the same setup when I first did my LS swap and still was the same. I decided to take it to a well known exhaust shop and he tried to explain all of the same things Joedoh mentioned.

Now I have an X pipe, the same Magnaflows just behind that and then the exhaust exits out the back. It sounds great, isn't too loud in the cab and no drone at all. So keeping the mufflers close to the headers is important and having at least some pipe after the mufflers also.

I also added electric cut outs for when I wanted it loud. Those don't sound good at all so they rarely get opened.

Re: Exhaust and Drone sounds
 

This Exhaust Damper fell off my Tracker last month. I didn't know what it was, so I went back and got it out of the road. I don't notice a difference, just glad the transmission didn't fall out next! I looked it up and it seems to be used for killing drone. You might try something like this.

Re: Exhaust and Drone sounds
 

All I can say for sure is i would never consider under vehicle exhaust again. The roar and rumble of 30" Glass packs out the back thru extra long pipes works for me.

Re: Exhaust and Drone sounds
 

A resonator in front of the muffler will kill the drone. I did this on my dodge ram with a super 40 flowmaster and a jones resonator. I have zero drone. On my 58 i plan on using black widow mufflers,which have very little if any drone. Currently the 58 has 2 flowmasters dumped before the axle and they drone enough.

Re: Exhaust and Drone sounds
 

Whats your resonator look like?

Re: Exhaust and Drone sounds
 

I'm headed to the muffler shop this week to get an estimate on getting duel exhaust put on my 49. The prior owner had the pipes coming off the headers into a single muffler and no pipe after the muffler. Muffler is right under the cab and very noisy. I was thinking of running the pipes over the axle then dump them similar to the pic. I like the pipes sticking out just past the rear bumper but what I don't like is seeing the pipe between the back of the truck and the bumper. Hope this works out ok.

Re: Exhaust and Drone sounds
 

I can see you wanting to keep it "clean". I have a huge black tow hitch "festooned" with a dump truck back up horn, backup lights and license plate so the extended pipes don't bother me in the way of clutter. They are suspended off the tow hitch so super strong. IMHO my sound is best ever and no drone. Love to keep windows down to listen and even neighbors say it sounds great. This next spring i am going to have either ventilated covers or paint to make exhaust look like read facing machine guns to go with the USAF theme.

Re: Exhaust and Drone sounds
 

I have full length headers, turbo header mufflers and duals going out in front of the rear tires. No drone. I do have only carpet on the floor. BUT, before I put the pipes on behind the mufflers and without any carpet I had extreme drone inside.

Re: Exhaust and Drone sounds
 

exactly how I want to run my, I have the gas tank in the bed between frame rails so can't go out the back. How do you like them turbo mufflers , I wish I could hear what they sound like

Re: Exhaust and Drone sounds
 

if no room for real duals, consider a larger pipe single, or a dual into single or a larger Y pipe into a single rear exit. quieter truck means you have your hearing longer plus a ride with a passenger to talk to and who likes and appreciates the ride, not one who smiles and says "cool" but then can't make a second trip.

you only get one set of ears. protect them. us old guys can attest to that. same for eyes. protect what you have. how many old guys have we seen who smile at everything we say, good or bad. like they heard everything you said. or how many can't read a darn thing without binoculars on.
"oh sick, you farted"---smile
"umm, you drooled on your shirt"---smile
"you have toilet paper stuck to your shoe"---smile
"uh, brocoli in your teeth"---smile
"ok, I'm gonna hit the can"---smile
"I think you stepped in something"---smile
"what do you think of those wheels?"---smile
yeah, ok, sometimes a smile would be an answer to these statements. sometimes the person simply didn't hear you and smiles just because.

Re: Exhaust and Drone sounds
 

My hearing is jacked , I have tindinidis and my ears ring 24/7.
I can’t go out back due to gas tank and shocks , exhaust guy would have to be a artist. I’m thinking borla with a resonator or the flow master 50 series with resonator

Re: Exhaust and Drone sounds
 

I have both hearing loss and severe tinnitus due to 18, 500 pound bombs going off low order after an F-111 crashed and burned. Lost count after 6 but they say it was 18 and low order means they cooked off and didn't fully explode as I wouldn't be here. The drone pitch and tone from the turn down pipes was absolute murder .

I thought i couldn't get rear exhaust either but the guy at my muffler shop really is an artist.

Went for cruise along the ocean today and really enjoyed it for once -- minus the drone.