spray or paint on sound reducer for underneath truck cab

[TomGolden]

Hi all,



I have searched the TDR Forums for every search pattern I can think of, and I have indeed found many posts on sound reduction techniques.



I do not necessarily want to sound proof my cab. I am after a very specific goal. I want to reduce or eliminate the awful drone I get in the cab between 1900 - 2500 RPM from my 4" straight piped exhaust. I absolutely do NOT want to try any mufflers, as every one I have ever heard will cancel out the awesome sound you get from being straight piped.



I do not really want to use any of the many types of mats (dynamat, ATP, Great Southern Insulation, or other similar products) because I don't want to have my truck down for days while I remove the seats and carpeting, etc. to install all the padding. This truck is my only means of transportation, and at most I would have one weekend to do this project. Hence my idea to try something that can be applied directly to the underside of the cab, something that can easily be painted or sprayed on.



I have also sent Greg L the "noise nazi" an email to ask for his suggestions.



Any other suggestions would be greatly appreciated.



Thanks,

Tom

 

[willyslover]

Tom. . a run through the mud bog might just do the trick

 

[Scot]

Check:

https://www.turbodieselregister.com/forums/showthread.php?s=&postid=470149#post470149

 

[Lsfarm]

I want it too!

Hi Tom, I want the same thing: a simple one step noise killer!



But the basic physics of the problem are just not going to be solved with a spray on or roll on product.



But Please! don't stop looking, I want to be proven wrong!



BTW It really won't take more than a day to remove the back seat, and the passenger side seat and cover the back wall and passerger side floor with a proven system of deadener mats, lead sheet or foam, or all of the above.



The other option is to have a custom made 4" exhaust made from pipe that is double the wall thickness of our available systems. this is where the drone comes from [in my opinion]



Good luck, I hope you find and share a magic spray on product



Greg L the Noise Nazi

 

[Steve Campbell]

I think I read...

where someone welded three 1" angle irons, spaced evenly, most of the length of the "Straight" section of the pipe and considerably lowered their drone level. You could try just Hose clamping them on, but that would not quite give you the same effect as welding.



A muffler shop owner I know, told me 20 years ago that when he builds a replacement muffler, the last thing he always does is make one continuous weld around the circumference of the muffler to eliminate the "Ring" that would have resulted with no weld. Maybe the angle iron does the same sort of thing to the straight section of pipe.

 

[Dane]

Tom,

Whatever method you use make sure you get to the back cab wall. I did mine from the inside with stick on sound deadener from McMaster-Carr and it's made a very noticeable difference.



Lots of road and exhaust noise somehow makes it's way thru the back wall. You don't realize it till it's gone. I wasn't real sure at first, but after a few months in different conditions I think it was worth the effort. It took me about 3-4 hours. Hardest part was getting the !@#$% B pillar covers off without breaking the attachment tabs.

 

[Clinton]

TomGolden,

You may want to check out this place:



http://www.quietnoise.com/nkillers.htm



I was doing some under-the-carpet wiring and found my matting soaked. The project shifted to leak detecting and I ended up with a gutted interior. At the moment I've shifted again to a noise reduction project. The link above is for a company that sells a product called 'Noise Killer' that was reviewed several months ago in Four Wheeler. I rolled on the first coat over the weekend (back wall, extended cab 1/4 panels and floor) and it seems to be pretty good, just going by knocking on the panels, I don't have any dB records. This stuff is water based, thick, and supposedly formulated for this purpose. It has the appearance of a bed liner when dry. You could do two coats over a weekend and be back together by Monday. I have some 'super foam' from GSI that I'll install after another coat of Noise Killer. As many have reported in the noise reduction posts that you've seen in the searches, there is nothing on the back wall, 1/4 panels, door panels, and floor. Doing anything at all will be an improvement.



So, I've spent about $400 on noise reduction materials ($48 a gallon for Noise Killer), figured out my rear window leaks, completely gutted my interior, and I still don't have the CB hooked up! Good luck.

 

[Clinton]

I guess I should have mentioned...

Forgot to say that I don't believe Noise Killer would be very good on the exterior. You would want to apply it under the carpet and behind the panels on the inside.

 

[700rmk]

cheap fix

Tom,

I have in the past on another truck done the following that seemed to help tremendously!!!





I had a Jardine 4" system with the muffler still installed and on the straight sections of pipe before the muffler welded some 1" angle to the pipe, helped a little bit, then I purchased some 4" muffler clamps from a local muffler shop and placed 2 evenly spaced on each of the straight sections of pipe, in my mind this changed the harmonic frequency of the pipes and reduced the noise. I still had a drone but it was from the muffler, I was going to take some threaded rod and bend my own clamp to go around the muffler but sold the truck before I attempted this mod. Give the clamps a try, they are cheap and removable, but I wouldnt weld again.



My 0. 02 worth.

 

[TomGolden]

Thanks guys. I had found an older post regarding the Noise Killer product, went to their website and tried to email them, but their address is no longer active. I'll try this new URL.



I will certainly let you all know what I end up doing.



I actually have tried the 2" angle iron clamped to the straight section of pipe. I have an 8' section of angle iron clamped on, and while it does sound like it helps some, I'd have to guesstimate it only helps maybe 10% at most... ... .



Thanks again,

Tom

 

[Clinton]

call 'em

at 1-800-634-4471. (I've still got the Four Wheeler sitting here at work)

 

[Mallory]

I did a few cheap mods that made a huge difference. First take out rear seat and put some mat up against the cab. Next weld a five foot angle to the exaust, I used 1"x"1 by . 125 . Next I had my trans out and coated the underside of the cab with several coats of 3m undercoat. I would spray it until it started to drip then let it dry and hit it again. Did it three times and it made a huge difference. Good luck!

 

[fest3er]

Re: cheap fix

Originally posted by 700rmk
Tom,
I have in the past on another truck done the following that seemed to help tremendously!!!...

I, too, had a *really* nasty drone at near 2300 RPM under part to full throttle with my 4" JRE exhaust with muffler.

I put *one* spare 4" clamp on the long pipe under the cab, judiciously placed to break up the long run of pipe.

The drone is no longer as annoying, though it is still there.

I would suggest installing two or three clamps placed so as to both break up the long length of pipe and also to avoid creating *new* harmonics and resonances. In other words, ensure that the distances between each pair of clamps are unique and not harmonic ratios of each other. That should eliminate the annoying resonance (or drone).

But if you want to experiment and be a little musical, you could try setting the distances to 1/2, 1/4, 1/8, making the longest distance, say, 4 foot. I may still attempt this at some point!

Fest3er