Recommendations for Sound Deadening/Insulation

[Warren99]

When I eventually swap the black interior into my truck I wanna put down some sound deadening/insulation on the floor, and since the doors will be gutted for the power windows I might as well put some sound deadening in them too. Any recommendations? Only real name that comes to mind for me is dynamat. I don't need the best of the best I can definitely settle for some cheap stuff.

[89 MJ]

If you’re going to do it, you might as well get the good stuff, IMO. Dynamat is where it’s at. 

[Warren99]

Thats kinda what I was thinking, which type of dynamat should I use?

[Pete M]

the main benefit from the added material is going to be the largest sections of echo-y sheetmetal, aka the roof and door skins.  the material adds mass to them to minimize the vibrations.  you don't even need to cover every square inch.  but you want a product that has thickness to it.  the more mass, the better.  I've seen some very thin offbrand crap on amazon that likely doesn't do much of anything in our trucks. 

[Airborne Janitor]

Dynamat is nice but they're real proud of their name. I used it in my XJ years ago, then used Kilmat https://amzn.to/3GPST7U on my MJ. No its not as thick as Dynamat, but it works just as well in my opinion and it's way cheaper.

 

 

 

 

[ghetdjc320]

Dynamat has a wide range of products depending on the application. There are several competing brands (noico, kilmat, sound skins etc) but few match the same deadening properties of some regular Dynamat Extreme (though something is better than nothing I suppose but you will get what you pay for). As Pete said, roof, door skins, b pillar, back of cab, all are good places to reduce the panel noise. They do not however “absorb” sound. They deaden the noises produced by those panels. My approach to sound deadening in an MJ is as follows: deaden any sheet metal panels that I can get access to including the hood, door skins, b pillars, roof, back of cab, inner firewall and trans tunnel. I then used 3/4 dynaliner on the firewall and 1/4 on the roof and back of cab and 1/8” dynaliner installed in place of the factory water shield. I no longer put down dynamat or any sort of butyl backed material on the floor themselves as you will inevitably trap some moisture at some point unless you stripped your truck down far enough to replace all the factory seam sealer and repair the worthless factory overlap seams and pinch joints. Mass backing on carpet will also disintegrate and turn to crumb over time not to mention it produces a horrible smell when it starts failing. If you need to deaden the floors use dynapad and trim it to fit almost like a floor mat but below the carpet. It’s a heavy material that does help soak up some sound but really helps with heat as well. Quieting down the cab also involves tracking down any little loose trim pieces or panes that can start to resonate or vibrate and either getting them all re-secured properly. Even proper door alignment and gaps along with good seals will make a world of difference in terms of wind noise at higher speeds. Good suspension bushings, rubber spring isolators all add up. Plus don’t forget to use a heat shield on the exhaust wherever it gets close to the cab floor and especially around the CAT if you have one. Keep in mind, this is not specific info for getting good audio system performance (although it will help to a degree) this is just to quiet down the cab of the truck for a more enjoyable ride. Audio performance has many other factors involved. There are also several area that have factory “pillar foam” and some areas where it’s good to add additional pillar foam. The back of cab brace to back of cab bulkhead is a good spot as is the inner rear roof bracing to roof skin seam and the a pillars. Basically anywhere there is a small gap between an innner and outer structure and filling it will not prevent access to water drainage or wiring. You’ll want to use the semi rigid (flexible) pillar foam. 3m and other manufacturers produce it and it’s a 2 part system. Plenty of videos online regarding use and application that can have a huge impact on cab noise. 

[Warren99]

1 hour ago, ghetdjc320 said:

 and especially around the CAT if you have one

Haha good one

Thank you tho, that is a lot of useful advice. I don't think I'm gonna get very in depth with it, I just figured since I'm gonna have the carpet, dash, and window assemblies out, might as well put some sound deadening so it's a bit quieter. Regardless it's gonna be a much quieter ride because right now my truck has no carpet whatsoever

[ghetdjc320]

Just now, Warren99 said:

Haha good one

Thank you tho, that is a lot of useful advice. I don't think I'm gonna get very in depth with it, I just figured since I'm gonna have the carpet, dash, and window assemblies out, might as well put some sound deadening so it's a bit quieter. Regardless it's gonna be a much quieter ride because right now my truck has no carpet whatsoever

Sounds good. Yeah i'd personally recommend doing the trans tunnel door skins, roof and back of cab. I'd just keep it off of the floors, or at least off of the uniframe caps or any other seams.

[75sv1]

I used B-Quiet in my Ford Contour SVT. At the time it was the closest to Dynamat. I'll probably go with Nico for the roof. I do have some Dynamat for the front doors, I bought at a thrift shop for $20. Also, looking at Lizard skin a spray on. ??? I might have used the B-Quiet in my '81 MB 240D. It already had some factory sound suppression. The 300D's had a sound barrier on the firewall in the engine compartment. 

[89 MJ]

I have Dynamat Extreme everywhere except the roof of my truck. High up in the b pillars, the floors, the doors, the floor, and the back of the cab. The product is heavy enough you should not put it in the roof, as it can make the roof sag or the adhesive will heat up over time and make the deadener sag. 

[Warren99]

29 minutes ago, ghetdjc320 said:

Sounds good. Yeah i'd personally recommend doing the trans tunnel door skins, roof and back of cab. I'd just keep it off of the floors, or at least off of the uniframe caps or any other seams.

Noted, I do live in the deep south so I'm not too terribly worried about rust and I should be fixing all of the water leaks I have right now, but if I do put any on the floor I'll be sure to avoid the uniframe caps. Still not sure if I will go with the dynamat or just get some cheap kilmat, although I'm kinda leaning towards that since being a senior in HS I'm still on somewhat of a budget, and I don't NEED the best of the best.

[ghetdjc320]

18 minutes ago, Warren99 said:

Noted, I do live in the deep south so I'm not too terribly worried about rust and I should be fixing all of the water leaks I have right now, but if I do put any on the floor I'll be sure to avoid the uniframe caps. Still not sure if I will go with the dynamat or just get some cheap kilmat, although I'm kinda leaning towards that since being a senior in HS I'm still on somewhat of a budget, and I don't NEED the best of the best.

Just remember, it’s very difficult to change down the road. That butyl is nasty to remove 

[pizzaman09]

Just last night I put 8mm killmat on my roof, it made a huge difference in roof vibration and even how solid the doors sounded when closed.  I will warn though, that extra thickness did impact fitting the headliner, it's now probably 1/4" farther forward than it used to be.

 

I used the Killmat because my friend had extra enough from his MR2 project to easily cover the Comanche's roof.

[Warren99]

32 minutes ago, ghetdjc320 said:

Just remember, it’s very difficult to change down the road. That butyl is nasty to remove 

butyl?

[Warren99]

12 minutes ago, pizzaman09 said:

Just last night I put 8mm killmat on my roof, it made a huge difference in roof vibration and even how solid the doors sounded when closed.  I will warn though, that extra thickness did impact fitting the headliner, it's now probably 1/4" farther forward than it used to be.

 

I used the Killmat because my friend had extra enough from his MR2 project to easily cover the Comanche's roof.

On that note would I be fine with something like 8mm everywhere or do I want more for the floor, doors, and pillars?

[ghetdjc320]

Dynamat and others are butyl rubber adhered to a thin aluminum sheet. The main difference you will see in how Dynamat performs is due to the thickness of the aluminum backer. The copy brands tend to have much thinner aluminum backing and some don’t even use aluminum as a backer. in other words, having thicker butyl won’t make nearly as much difference as a thicker backer. They go hand in hand. It’s not just a name brand that is trying to ripoff the customer, in fact it’s quite the opposite. The copy brands tend to be the real ripoffs. Don’t get me wrong, you can find some good quality products from other manufacturers but you’ll be paying about the same amount. 

[Warren99]

oh ok

[Pete M]

just want to reiterate that the vast majority of "quieting" that you can achieve will be from a few sheets slapped on the roof and inside the doors (on the outer door skin) or inside the b-pillar.  after that you get quickly diminishing returns because large "echo-y" panels transmit most of the noise (because they are free to vibrate), while the formed panels with lots of bends and wrinkles like the back wall or floor transmit far less because they have stiff structure to them. 

 

side note, when I do a project, a guiding thought in the back of my head is: don't create future headaches.  I can't even fathom the work needed to remove a whole mess of that stuff to fix something.   

[Warren99]

Yea I likely will just skip the floor then, the donor MJ actually still had the like cloth insulation under the carpet. I'll be using that regardless, I just need to get all of the giant shards of rust off the bottom of it.

[Pete M]

I would probably skip that horribly cloth padding for something that doesn't absorb water.  I know I've seen people suggest things, but can't remember any off the top of my head.    in fact, I should probably find out since I'm in the middle of a very similar project to yours. 

[pizzaman09]

10 hours ago, Warren99 said:

Yea I likely will just skip the floor then, the donor MJ actually still had the like cloth insulation under the carpet. I'll be using that regardless, I just need to get all of the giant shards of rust off the bottom of it.

Your truck sounds like mine.  All original components at 250k miles including the heavy pad under the floor that has lots of rust chips stuck to it.  When I get to recovering my seats I'll rust proof the floor and probably replace the pad.  Also don't forget to use the opportunity to replace your parking brake cable.

[Warren99]

If the cloth absorbs water and the sound deadening traps it, what do I do just leave it bare underneath the carpet?

[ghetdjc320]

1 hour ago, Warren99 said:

If the cloth absorbs water and the sound deadening traps it, what do I do just leave it bare underneath the carpet?

Great question. Neither is good but ultimately, you want to avoid leaks in the first place. As long as you don’t cover over any factory seams or seam sealer and you use a roller to really apply the Dynamat (or other brand) well, there should be no water trapped under it. As far as water absorption, again, you don’t want there to be a water source to absorb in the first place but, absorption also means there is a “wicking” effect and little by little it will evaporate. Trapping water is much worse in that scenario. Here is how it’s worked for me in the past: I bought a nice acc carpet set for the MJ with the mass backing thinking it would also provide some nice sound deadening and maybe even thermal insulation. I also applied Kilmat to the floor and did pretty much the entire floor with it. About 2 years later I had epic rust out through the floor. It came in both up through the seams in the floor under the factory seam sealer and was trapped under the kilmat and it also came in though a couple of cab leaks (rear window and around blower motor seal). That water got trapped on top of the kilmat and under the mass backing where it became a haven to mold, mildew and every sort of vile microorganism imaginable. I documented the repair in my 91 Eliminator build thread. The repair was very extensive and I learned many a place where the MJ was very poorly assembled and just asking for rust trouble. It’s true what they say, these trucks rust from the inside out. Anyways, after new floor were replaced, all the factory seam sealer removed and all the joints repaired and sealed, I installed regular carpet with no mass backing (just the regular jute backing in certain areas) and limited the Dynamat to certain panels that had no beads. Any panels that have design or structure elements to them (beads) will not have nearly the same panel vibrations as the big open panels like the roof and door skins. In summary: You can strategically place your sound dampening materials in an MJ to get the best result. Also, don’t be concerned nearly as much with items that can absorb water. Avoid trapping water by installing some impermeable barrier that will not allow any wicking or absorption. Just my $.02 for what it’s worth. 

[Pete M]

The padding underneath is heat insulation. You might notice if it's missing. 

[WahooSteeler]

I put Noico 80 mil in my truck and was very pleased, especially at the price on Amazon. I just read a review on a product called Soundskins that is a 3 layer product vs the typical 2 layer of butyl rubber and aluminum backing. A bit pricey but got a good review. 

 

https://www.motortrend.com/how-to/soundskins-sound-deadening-wrangler-jl/