Sound deadening question?

[Biker 10+ year member]

I have a dodge dakota Club Cab and will start my Dynamat project this weekend.

My question is in the back seat under the side panels there are holes going into the body. There are no windows or anything in there. I could cover the outer skin with Dynamat and then cover the holes and dynamat the inside panelssame as I will do on the front doors.

Could I save money by putting some instalation foam in there or foam rubber or something other than expensive dynamat. I really need to deaden this area as there is a lot of road noise coming from that area and a lot of vibration outside there when the music is loud.

Thanks for any suggestions.

Biker

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[Biker 10+ year member]

Help please?

 

[Decipha 10+ year member]

fuk dynamat... raamat that bastad

sure thing... foam will work for large gaps

 

[chucku 10+ year member]

Some people use plexiglass or mdf to cover the hole then dynamat over it. Dynamat extreme is good stuff, just expensive. It cost me $400 just to do the doors and rear wall of my truck.

 

[Biker 10+ year member]

What I am talking about is the large area behind the doors when you remove the side panel just below the back windows.

If I purchase can's of spray insulation foam at home depot to fill that area and then cover the inside with Dynamat will it be just as good.

Maybe Im not clear. OK with the doors you have to put Dynamat inside and then again outside because theres a window in between going up and down but the same area in back doesnt have anything in there so I want to fill the area with the cheapest whatever?

Thanks

Biker

 

[helotaxi 5,000+ posts]

Expanding foam will work fine for that but it is very permanent.

 

[Biker 10+ year member]

Thank you very much, I cannot for the life of me think of any reason I would need the foam out of there.

It is the area right now that vibrates the most when I turn up the Bass. The area is so hollow and the outer skin so thin it almost acts like a speaker when your outside of the truck.

Thanks again

Biker

 

[mlstrass 5,000+ posts]

Could also use sheet metal and self tapping screws to seal it/make it thicker, then deaden over that. That's how I did the large holes in my doors...

 

[Biker 10+ year member]

I will be covering all the holes with sheet metal and sound deadening the entire surface but need more than that. As I understand it the normal proceedure would be as follows.

1-Sound deaden the entire inside (Outer skin) with several layers of Dynamat

2-Cover all holes on the inside as you stated above

3-sound deaden the entire inside

4-replace plastic wall panel.

All I was trying to do was save the money spent on Dynamat on the inside so I will fill the entire inside with expanding insulation foam then cover the holes and Dynamat the inside.

I just hope it works as well as Dynamat because as stated above it would be a B***H to get the foam out and start over.

Anyone have heartburn with this plan please speak now before I pull the trigger.

Thanks Biker

 

[audioholic 5,000+ posts]

I will be covering all the holes with sheet metal and sound deadening the entire surface but need more than that. As I understand it the normal proceedure would be as follows.
1-Sound deaden the entire inside (Outer skin) with several layers of Dynamat

2-Cover all holes on the inside as you stated above

3-sound deaden the entire inside

4-replace plastic wall panel.

All I was trying to do was save the money spent on Dynamat on the inside so I will fill the entire inside with expanding insulation foam then cover the holes and Dynamat the inside.

I just hope it works as well as Dynamat because as stated above it would be a B***H to get the foam out and start over.

Anyone have heartburn with this plan please speak now before I pull the trigger.

Thanks Biker

Its rear doors, with no windows that move up or down, correct?

Just be sure that when you fill the area with foam that you do not obstruct 1) drain holes for rainwater, do not create a water trap, and 2) any door/lock mechanisms.

Lastly, apply the foam in stages. If you try to fill the whole cavity at once, you are more likely to overfill the area, or worse yet, leave undeveloped foam in the center, that WILL expand later (probably on a hot summer day). If this happens after you've already filled and sealed the space, something will have to give, including possibly popping a body panel out into a deformed shape. Be VERY careful using that foam.

If you want a cheap mass loader that works well on outer door skins (on the inside), try mixing concrete and Kool-Seal. It makes a nice sticky concoction that will stick to sheetmetal, stay stuck, and add mass like no product on the market possibly can.

 

[Biker 10+ year member]

Ill never do that again. There was a fairly large area to fill so I thought the foam would be a low cost solution. After spraying 12 cans in there I have a very good insulated area now and the area is very solid with great success.

But at $6.00 per can I didnt save any money for sure. It was like after spraying 4 cans how do I stop and start applying the Dynamat. Decided I couldnt so with 2 more trips to Home Depot I finally filled the entire area.

Thanks for all the help.

Biker

 

[helotaxi 5,000+ posts]

Did you lay down a layer and let it expand and cure a bit before doing the next layer?

 

[audioholic 5,000+ posts]

Did you lay down a layer and let it expand and cure a bit before doing the next layer?

God I hope he did. Its not like I didn't mention it before he did it. //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

12 cans sounds like alot.

 

[helotaxi 5,000+ posts]

12 cans sounds like a whole lot. I filled the kickpanel in my old truck complete with part of the area between the fender and fender-well with about 1/4 of a can.

 

[Biker 10+ year member]

Its a long story but the first 4 cans were a brand that guarentees no buckling of sprayed areas. Yea thats because that stuff dont expand much. The next 4 cans were even worse. It was like a spackling compand that may have worked good if I just sprayed about a 1/2 inch everywhere but no I wanted that area filled. so finally I got the good stuff. Big Gap Filler. those 4 cans expanded good and its seems to be real good now.

I did my left front door today with Dynamat and Ensolite and could not believe how much different it sounds while driving down the road. One more door to do tomorrow and it will be like turning a Dodge Dakota into an Escalade. Will as far as quietness is concerned.