In that case @Jo7.3 feel free to post that big long pm i just sent if you think its useful, My sent pm's automatically delete themselves

 

So I gather some data, tab delimited, I look at in Notepad....I see some "issues" at 80Hz and lesser at 160Hz.

I want to graph (heck, even just view it) it so I import it to Excel....Now nothing shows in the 80Hz range. All in the 160Hz.

 

Sorry for the late response guys, really busy at work today. Anyways, here's the response that @KubotaOrange76 sent me. Lots of good info and thanks for taking the time to type it all up!





The longer 51" Donaldson is even better, but can be a little more difficult to fit under your truck depending on the length. They offer a 51" with a baffle in middle and also a straight thru version like the 40" i posted. If you think about it, pretty much all your typical trucks pre cat and dpf are running one of the versions of the 51" in the 5". The jake is significantly louder on the non baffled one but they offer max flow and no drone with a little bit of sound out the exhaust. I feel like Donaldson did a great job of the design of this muffler, max flow for 12-15 liter motors with no drone and minumal noise at a low cost. I ran a 51" on my 2007 dodge as well and liked it, but it was too quiet for my 23 year old butt. I probably ran 6-8 different muffler setups on that truck and landed on the 40" and left it on there until i sold it. Ill link a few old crappy youtube videos so you can get an idea of the difference. Its hard to tell because the camera doesnt pick up the deep tone very well.

I recommend buying at ryder fleet products online, i always had great luck with them.

Keep in mind the inline 6 diesels like this 5.9 are much louder and more prone to droning in the exhaust department than these 7.3's, Ive never had a 7.3 that i had an issue with drone on except my 2003 which is straight piped, but its barely even noitceable

here is first example for comparison - typical short straight thru muffler that droned like crazy loud inside and outside (please bear with me these videos were shot in 2007-2008)

Next with a 4" 51" donaldson, basically sounded like a big rig going down the road

And the 40" which isnt as loud as you think, it just had a nice deep tone with a little turbo whistle


The OBS 3.5" 7.3 mufflers are very similar to this inside but shorter, with a cat delete they are still quiet inside, Im probably going to end up putting one i have laying around on my 2003 before its over with

 

Personally, I think I'm gonna give the 40 inch straight through muffler a shot. I'd still like a little bit of exhaust noise on the outside, just want to cancel the drone on the inside. I also have an extended cab shortbed truck, so I think it'd be a little cramped with the 51 inch muffler.

Also, kind of off topic, but hopefully helpful. I got to lookin at the fertilizer truck I was driving today, and it's equipped with an m11 cummins. The exhaust runs right up beside the cab on the passengers side and has a muffler that looks a lot like some of the donaldson mufflers. I'll look at it closer tomorrow to see if it is indeed a donaldson muffler or not. As far as noise, with windows down, yeah, it's pretty loud, but it has a nice tone. The exhaust is like right near the window after all. With the windows up though, all I hear is tire noise (it's got like 48 inch flotation tires) and motor noise. So whatever muffler is on the m11 truck does a solid job. There's no drone other than tire drone with the windows up.

 

Well, I gave the 40" a try. Initially I was gonna cut the FTE resonator out and install the muffler in its place. However, the muffler was too big in diameter to fit where the resonator was. So, I left the resonator in and had the muffler welded in place right behind the resonator. Now as far as sound, it is very quiet inside and outside. There is still just a very very very small amount of drone right around 1800rpms, but it's not enough to bother me and honestly, it sounds like it's coming from the resonator. For example, when I'm sitting in the cab, I can hear the most drone coming from under the passengers seat which is about where the resonator is in the system. This brings me to my next point...I'm gonna cut the resonator out and run just the muffler and see what it sounds like. I was debating on doing this today, but wanted to see what it sounded like with both resonator and muffler installed. Both the resonator and muffler combo is a bit too quiet for me (I am only 22 so I like a little bit of noise). On the outside of the truck, I have to lean down next to the exhaust to hear any kind of exhaust note. Inside of the truck, I only hear turbo and engine noise. Will try and get some pics and a video tomorrow.

 

I look forward to seeing/ hearing results

 

My drone seems to have calmed down, still there but not as noticeable.

 

That's good to hear. My drone problem has now gotten a bit more complicated...As quiet as the exhaust is now, I really don't think the exhaust is what's causing my drone. At idle, I can hear a very slight vibration that I can't quite pinpoint where it's coming from. Definitely sounds like it's coming from the drivers side somewhere in the engine bay, but I can't tell exactly where. Also, with the engine idling, I can feel a pretty good vibration on my AIS intake. It's vibrating enough that the words "push to reset" on the filter minder are blurry until I put my hand on it which stabilizes it. Along with that, the whole exhaust system vibrates pretty bad, but I'm not sure if it's because of the vibration from the engine, or what. Is it possible I have a worn motor mount on the driver's side? I do have a clunk when putting the truck in reverse, and then also when going from reverse to drive. I also have a very slight clunk when coming to a stop. I know it's not the slip yoke cause I just greased the crap out of it a few weeks ago. If it is possibly the motor mount, anybody know a way to check for sure that it's the motor mount? Thanks for all the help guys!

 

Id say start you a thread and lay out all the facts for the great minds here to weigh in on

 

This was a great thread. Did any of you try any of these ideas out? When I am towing or even in my truck for 2+ hours the drone is really tiresome. I have had the internet claimed "drone free" Magnaflow 4"/3.5 DP system since new - either I am getting older or the old Magnaflow muffler is not working as well. I have had a 30" FTE resonator sitting in the box for years, but every time that I have thought about installing it (and the subsequent cutting up the current system) I just can't bring myself to doing it, Not only does the FTE look like a cork, it also seems to be a bit of Voodoo engineering as that design has never caught traction with anyone else formidable (OEM's, bigger name after market, etc) over the years. I have personally experienced the Helmholtz resonator on the intake of a different vehicle and they do work very well. I think on our 7.3's it is on the exhaust side and especially prevalent for those of us who have bigger diameter systems installed.

 

A few heat cycles on the new exhaust and the drone went away.

Never had to fab the Helmholtz.