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Discussion Starter #1 (Edited)
What is it about that Diesel 4BT sound that we like so much? Is it that we know everyone who hears a diesel know that we can beat the snot out of their gasser in a power play?
I diverge.

I know we all like the sound of our 4BT's but what is everyone doing about sound insulation or is it that you just don't care?

I personaly just made an amazing improvement in my cab noise level and I want to share it with everyone here.

I was taking my son out to pick up a new hood for his Honda and I thought I'd ask him, as a passenger, where he thought the engine noise was coming into the cab. My first thought was that he would point to the foot well under him since that was where the 4" exhaust ran only 1/2" away. He leaned over and said it was loudest near my transmission and transfer case shifter boots.

Last night I took off both boots and proceeded to lay down four oval shaped layers of carpet inside each boot. I made sure that the layers were held tight to the metal tunnel opening surface when I was finished.

Today I ran the truck to work and could not believe the sound level difference.

Incidently, one day prior to that I glued down another layer of roofing shingles to the passenger footwell. I have found a very noticeable reduction in noise level. My searches on the TDR site back in 2004 when I started my engine swap indicated that sound is deadened by mass (and I mean something with weight to it). I knew that shingles resembled the material that some of my past cars had under the carpet. The second most important factor in noise reduction is that you give the sound something to extend the time that the sound ricochets between to absorb the energy into. This means alternating layers of dense material with softer layers of something else. If you study some of the more expensive sound deadening product out there you will realize that you can do the same thing with common building materials.
Who needs expensive Dynomat?
 

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Discussion Starter #3
I know the dynomat product works well for diesel vehicles. No offense intended. I just found another way for those who cannot afford the extra cost of Dynomat or want to use the saved $ on that new intercooler.
 

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But isn't part of the joy of running a Cummins the SOUND?!? bounce
You can always open the window! I presonally just used a few cans of under coating on my truck, I figured i should before the motor goes in this one I'd hit the firewall, under the cab, the fenders, and possibly the hood yet. I'm pretty sure it will work well because this truck actually has fenders and a hood on and is sound deadend better from the factory and the previous did not... and it won't be dumping the exhaust right out under the cab bounce
 

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Interesting idea, DW. On mine I simply used heavy re-bond type carpet pad over the heavy steel flooring and firewall. I rebuilt firewall and floors with some steel plate that's about 1/8" thick which helps, plus carpet and pad quiets it down even more.

We know that sound waves reaching the ear got there by changes in air pressure sensed by the ear drum. Medical sience is still puzzled at the wonders of this part of a man's creation because of its astounding complexity!

Anyway, one has to address any issues of outside air entering cab from below, like at door seals etc. I had some large voids at lower door sides and bottoms that I filled with a heavy rubber weatherstrip and the difference was amazing! Now I can talk back to the 'little voices' without yelling :idea:
 

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Discussion Starter #8
I remember one guy over at TDR that said he was not worried about loosing his hearing cause when he did loose it then he wouldn't have to worry about insulating his truck.
I'm so tickled about this noise reduction that I may just go out and buy a radio for the truck now that I can hear one.
Ah. Rebound carpet.
I still have not put a carpet in yet. Hell, I'm sorta liking the look of those shingles now. I may never put carpet in. When I look at my shingles all glued down I can really say "It POPS!".
Gees, That sounds like one of those gay designer shows on TV that you have to click the channel changer past real fast.

I took Decibel readings inside my truck about a year ago and reported them on the TDR site. I will try and borrow that meter again and see how the numbers have changed.
 

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I did some spray in bed liner in my cab that I thought would help but didn't too much. The big difference with bed liner is getting professional 1/4" stuff sprayed in, not cheapo DIY stuff like I did.. But I plan on sound proofing with matting
(check out this link, the best info out there:
http://www.sounddeadenershowdown.com/ )

Then I plan to put some carpeting over that. Also good weather stripping goes a long way. My last truck was a tin can and loud as all hell.. Could barely hear the cell phone.. This one will be nice and tight and quiet...
 

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I used 12" x 12" Q Pads on the firewall and floor. Heavy insulation in the body side walls. Then put good carpet on the floor and firewall.
In 1,2,3 gears she is a little nosiy. Once in 5th I can push in the CD and enjoy the tunes.

Paul
 

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Discussion Starter #11
Anyone doing anything special in the doors that made a big difference?
 

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Anyone doing anything special in the doors that made a big difference?
I have been pondering using the high density sponge plastic that goes under the new style simulated hard wood flooring. It is about 1/16" thick and it seems to be waterproof and would act as both a sound deadener and insulation.
 

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I have been using Heat / Air duct insulation comes in different thickness ,you can all so put this in your doors as well.

Check out Lowes,Homedepot.

Thanks
Scott
 

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1989 Jeep Wagoneer, 360v8, 727, stock for now,
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I've used quite car in combonation with Accumat
bought through JC Whitney, cheaper that way. There's also Cab Insulation that I might use, but havent yet. Also have some cab insulation for the engine that havent used yet
Thers also B-Quiet that havent used but is on my list.
I went from 87 DB (A scale) with just Accumat on the firewall and under the hood . Added quiet car under the cowl and went down to 85 DB. These measurement were taken at 65 mph. The problem I see now is wind noise coming from lack of a good seal on the doors and windows. My goal is 75 DB which is what I measured on my wife's 94 CTD at 65 mph.
All measurement done with this DB meter.
I still have all of the floor pan and doors to do when I can get to them.
 

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Has snyone done anything with their hood? Like i said in my previous post I plan to at least try it, because it seels like a lot of noise is through the upper part of the cab so I figure a little deadening of the hood could go a long way! Maybe I'll do a before and after even though it is more hassle...
 

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Huh? Can You Talk Louder?
 

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In snow country here there is a roofing product that is called ice shield. Its a bituminous roll 36" wide that is installed directly on the roof decking at the eaves and the valleys. It bonds itself to the wood and keeps water that may back up from an ice dam getting thru the decking. Anyway, it works great on the floor or on the inside of doors. It bonds itself to clean surfaces. On my F350 I used the B-Quiet foam stuff with the layer of lead sandwiched in the middle. None of these products will make a diesel as quiet as a gasser under acceleration. On the highway at 70 my truck is almost like a Mercedes. The sound deadener not only almost eliminated the engine noise but also the road noise from the tires. It makes for a much more enjoyable ride on a long trip but there is no question its a diesel under acceleration. Of course the 4" straight thru exhaust may have something to do with that.
 

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1989 Jeep Wagoneer, 360v8, 727, stock for now,
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Has snyone done anything with their hood? Like i said in my previous post I plan to at least try it, because it seels like a lot of noise is through the upper part of the cab so I figure a little deadening of the hood could go a long way! Maybe I'll do a before and after even though it is more hassle...
I used Accumat Absorber under the hood. Its .750 in. thick. I cant find my notes, but I think it was worth about 1 DB reduction inside and outside.
 

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Seriously, if you guys have the time, check out the link I posted.. They test and review all of the different sound deadeners, price and all..
http://www.sounddeadenershowdown.com/

I also emailed the guy about some of the air duck stuff, he said a lot of the deadening and quieting is from good contact and absorption with the metal it is attached to. So the air duct stuff might be a good second layer... The ice shield roof stuff works well and is identical to the cheaper stuff the deadeners sell.. It is cold here in Utah but hot as hell here sometimes too, especially in the south during warmer months.. I hear the asphalt based stuff can sell like tar at higher temps on warmer days.. The big reason I am hesitant to use it. Again plan is deadener, couple layers, good weatherstipping, carpet, and tight boots around the cases, hopefully that will help. I rattled my brains out last time but had poor weatherstripping and no insulation/proofing whatsoever, I was basically driving a '71 tin can on wheels :D
 
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