# Under body sound deadeners?



## crzystng (May 2, 2008)

I have a lifted 96 Cherokee sport and a few years ago I gutted her to install >220^3 of Raammat. Well I also installed a flowmaster Delta 50 muffler along with a hi flow cat and header, amongst a few other go fast goodies and I am getting a lowish frequency drone that is going to drive me insane as it is impeding on the overall SQ. (Ya I know, JEEP-SQ LMAO) Because it is lifted with bigger tires I also STILL get a lot of road noise that comes through the cabin that raises the noise floor so loud that I have considered selling her and starting over with a luxury car, that is until winter hits and I realize just how much I love having the ground clearance and 4WD. 

Now my plan so far is to use something to undercoat the uni-body and HOPEFULY get the noise to a reasonable level. I am just not sure of what kind of products to use, or even what all is really out there. Truck bed liners, spectrum?? I just don't know what is going to give the results I am really after here. I have a back injury that is VERY limiting on the amount of work I can do at this point, but I would love to strip the interior AGAIN, (ya right lol) and go back through with some more mat and a few cans of expanding foam. I'm just not sure how far I will be able to get with the lifting and wiggling around I will have to do ya know.


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## basher8621 (Feb 21, 2009)

The spectrum from SecondSkin will deffenitly work for you.


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## bakkenar (Jun 8, 2010)

i'd throw some ensolite under the carpets too...


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## basher8621 (Feb 21, 2009)

I have never used ensolite. I have Luxury Liner Pro under my carpet and it does very well.


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## katodevin (Feb 14, 2008)

Also look into mass loaded vinyl (MLV) and you'll see that deadener mat by itself does very little at blocking airborne noise like you are experiencing. Almost all companies reccomend using a deadener (raammat) along with a decoupled layer of MLV to get the full sound barrier you need.


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## AAAAAAA (Oct 5, 2007)

Only problem after sticking all that stuff under the floor is to put everything back on top and make it fit.


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## thehatedguy (May 4, 2007)

LLP is foam with a vinyl barrier on top.



katodevin said:


> Also look into mass loaded vinyl (MLV) and you'll see that deadener mat by itself does very little at blocking airborne noise like you are experiencing. Almost all companies reccomend using a deadener (raammat) along with a decoupled layer of MLV to get the full sound barrier you need.


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## katodevin (Feb 14, 2008)

thehatedguy said:


> LLP is foam with a vinyl barrier on top.


Yep, that'd go well with his existing layer of raammat.


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## crzystng (May 2, 2008)

One question I have concerning the Spectrum undercoating is how well will it hold up to the elements being exposed and all? Most, if not all of the pictures I have seen of this stuff, it is used on the interior of the vehicles as more of the mass loading typed stuff vs. actually under the body. Where I live the JEEP gets used primarily in the winter time and they like to use a ton and a half of road salt/sand, which is going to make prepping a royal PITA lol. How will it fair against say the cheaper wax or asphalt based undercoating's in terms of longevity? $30 a gal vs. $75 ya know. Also, how much do you think it would take to cover the undercarriage of the Cherokee with the required thickness? 2-3 gals maybe?


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## thehatedguy (May 4, 2007)

Ant recommended to me to use the Spectrum as an undercoating for my Lexus IS300. With the Spectrum on the outside and the mat on the inside, you sandwich the metal and get a multiplicative increase in efficiency of both. He said 3 gallons to do the whole underside of my car and wheel wells would do it.


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## sqshoestring (Jun 19, 2007)

I remember the first time I worked on a 944, and drove it back from the frame shop. Dang little car was quiet. I found out why, the entire bottom 8" of the car was coated with the toughest gravel guard stuff I ever saw. I had to grind a spot and had a hell of a time. It was less than 1/8" thick I'd say, and I have no idea what was under the carpet.

My buddy was telling me about a place that sprays the bedliner on. The guy will spray anything, he even did the roof of a house. Does sub boxes, you name it he will spray it.

Or, try a different muffler.


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## crzystng (May 2, 2008)

See that's just it. I have heard a few peoples thoughts on what a simple bed liner can do for "deadening" a vehicle when used as a undercoating, and I think we can all agree that stuff is damn near bullet proof, so longevity due to exposure of the elements, along with other elements from wheeling the JEEP, would not come close to breaking it down. IDK, stuck between a rock and a hard place. On one hand I need something that's cost effective, yet is going to tackle the job with ease and not break down later on, possibly. 
Trust me when I say it's too much work to get that muffler out, plus it pulls double duty as a skid plate, hehe. Besides I kinda like the way it sounds, just on the OUTSIDE. :laugh:


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## bakkenar (Jun 8, 2010)

crzystng said:


> Besides I kinda like the way it sounds, just on the OUTSIDE. :laugh:


Oh, so you're that ******* who annoys everyone else but doesn't want to be annoyed themselves... nice :laugh:

Just kidding, those inline 6's aren't that loud anyways. A buddy of mine wracked his muffler on a rock and so we just sawzalled it off.. it wasn't even that loud. I'd do the bedliner on the bottom thing they were talking about


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## crzystng (May 2, 2008)

bakkenar said:


> Oh, so you're that ******* who annoys everyone else but doesn't want to be annoyed themselves... nice :laugh:


I don't get to drive the JEEP very often, (< 1K in 2 years) but when I do I imagine it being like when Joe down the street pulls out the corvette for a few good rides, except my summer rides are more in the winter, and WTH goes around in <30*F weather with their windows down anyways? LOL Like you said though, these I6's really aren't that loud anyways, even if it is poked and stroked :evilgrin: 

:idea:You know, damn, I just realized WHY the exhaust drone is louder than it really should be, and do I feel like an idiot. Because of how the suspension articulates in the rear and the close proximity of the exhaust to the springs, I decided the best thing to do was to weld everything from the muffler back, to the frame. I can almost guarantee that THOSE vibrations are being transferred directly into the cab thus giving me that noisy annoying drone. :facepalm:

Back on topic though, anyone have any real world experiences with using bed liners as undercoats/sound dampening? I am really leaning that way as there are a few places around town that can do it for fairly cheap, which would save me a ton of work and back ache. Not to mention, it might actually get done :laugh:


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## ANT (Oct 15, 2005)

Bed liners are terrible sound deadeners.
They are not elastomeric and not abl to convert the vibration in to heat like viscoelastic coatings and constraint layer dampers do.

They are amazing undercoatings, but terrible noise dampers.
Wanna see how well a bed liner stops vibrations?

Take a small hammer to a truck bed that has a bed liner on it.
The entire truck bed will still vibrate. With a real noise coating, the difference is night and day.

Coatings like our Spectrum product are great for reducing vibrations and some (some!) airborne sound waves. They formulation in the Spectrum coating is not too far off from our mass loaded vinyl barriers. Just differnet resin and more addatives..

The only time I suggest using a noise coating as your only means of sound deadening is when:

1. The customer does not want to take out the interior of the car, and ONLY wants to treat the underside.

2. They have alreayd treated the interior with a vibration damper, and a noise barrier and still desire more noise reduction

3. The entire interior is stripped out (usually an old street rod or restoration) and they want to spray the entire inerior.

Noise coatings are great, but I prefer to use them as a compliment to CLD Mats and MLV Barriers.

ANT


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## crzystng (May 2, 2008)

THX ant for helping set the record straight. Hell of a sales pitch too  LOL I know what I NEED to do, now it's just a matter of acquiring the funds to do so and tearing into the JEEP AGAIN


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## mastermind (Jul 11, 2010)

Spectrum looks like just the thing I've been looking for in the way of an undercoating. When used as an undercoating, how long should someone wait after application to drive the vehicle? I couldn't tell from the product FAQ or the video what would be the best timing.

Keep in mind, I'm in Seattle, so wet roads are pretty common.


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