Sound deadening for trunk

[vanceboy]

I posted an earlier thread about the horrible exhaust drone I am getting in my 69 charger and got recommendations for quieter mufflers and/or resonators.

I stopped by a muffler shop today and will get that taken care of.

I am also convinced that a lot of the noise is coming through the trunk floor and rear seat as it sounds like there is a 12" speaker blaring right behind my head at 50 mph.

I bought some self-stick sound insulation off of amazon for behind the rear seat and package shelf.

I also want to do something about that huge metal trunk floor right above the rear exhaust. I'm sure that's acting like a huge diaphragm and magnifying the sound.

I am aware of products like Kilmat, Fatmat and Dynamat and other sound deadening insulation. The problem is they will all adhere to the trunk floor.

I don't want to do that for fear moisture will get trapped under the matting and start rusting the floor. I would like a sound deadening trunk mat that is removable.

Has anyone heard of or made anything like that? Or does the sound deadening mat have to be stuck to the surface to work?

Any info would be greatly appreciated!

Thanks Vance

 

[Photon440]

Unless you have a leak coming into your trunk, moisture under the adhesive matting won't be an issue.

 

[Charles Cook]

Take you’re trunk mat and turn it over, apply the sound deadening to the back of the trunk mat and reinstall. That way there’s no sticky on the paint and if you don’t like it buy another mat. No harm no foul.

 

[OMTWF-72SE]

Along with muffler and resonators, if you have turn downs and they aren't past the rear valance that bounces sound back into the car. Do you have the mdf/fiber board panel mounted between rear seat and trunk. I can't see from the picture.

 

[vanceboy]

Along with muffler and resonators, if you have turn downs and they aren't past the rear valance that bounces sound back into the car. Do you have the mdf/fiber board panel mounted between rear seat and trunk. I can't see from the picture.

yes. fiberboard is in place

 

[vanceboy]

Take you’re trunk mat and turn it over, apply the sound deadening to the back of the trunk mat and reinstall. That way there’s no sticky on the paint and if you don’t like it buy another mat. No harm no foul.

Yes, That might work. Just wondering if the sound deadening material has to be affixed to the surface you are deadening or if just placing it on the surface will also work.

 

[Donakey]

That’s a great idea Charles I second that. I’m doing the same gives the mat some more rigidity and fits perfectly

 

[Carcinogen]

I addition to dynomat, this hytechsales.com/sound-absorbing-paint or a homemade paint/microsphere mixture is used to reduce vibration/sound.

Can also be used to reduce drumming of trunk lid. Take it off, tape up openings and put paint mixture inside and rotate lid around to spread paint on the inside. Trunk will have solid thud when shut.

 

[440 4 speed]

It would be worth a try to get melt or some similar material from an upholstery shop and lay it in. Not expensive,

 

[j-c-c-62]

The purpose of the material sticking to the metal makes the metal think/act like its thicker/heavier which is the process by which it lowers/dampens the resonance that is excited in your "drumhead" trunk floor. You could also use a pick up bed like heavy coating that would not allow moisture entrapment, and do both sides if max results are desired, and leave the insulation loose and throw/glue carpet onto the loose insulation. Removing the bed coating would be a chore as we all know. Not sure I would go to that extreme.

 

[Mopar Hunter]

Earplugs.

 

[AR67GTX]

I’m not sure it’s worth the effort. To shut out some intermittent gear whine I tried insulating off the trunk from the cab - sound deadener on top of asphaltic vibration mat under the rear seat up and over the top of the axle hump, divider board lined with sound deadener and insulation mat, sound deadener under the package tray, even formed fiberboard block off plates with sound deadener and placed in the cavity leading over the wheel wells into the rear quarter window spaces. I can’t tell any difference. Fortunately, except for some vibration mat under the seats, I used SA foam board sound deadener so I didn’t add much weight.

 

[70 sublime]

We have a roll of insulation that is like tin foil on each side with the foam air bubbles in the middle
Got it when doing some cement work to lay on the dirt and put water pipes on to heat the floor to reflect the heat upwards before the concrete went in
Something like that or some of a carpet store under lay you could try under the carpet to see if it will make a difference and easy to remove if it does not work

 

[Charles Cook]

You could try some carpet jute hair pad like I have. Works good and like mentioned above, you can remove if you don’t like it.

 

[1967coronet]

Im sure you have but, one more thing is trace or follow your tail pipe routing.
Make sure they do not contact any part of the car except the hangers.
Also make sure all hangers are tight at the mounting point and insulated/rubber hung.
I also like Charles idea of back side of trunk mat applied sound proofing.

My 67 always had a drone that I was used to. The muffler swap made a big difference.

 

[68BabyBlue]

Take you’re trunk mat and turn it over, apply the sound deadening to the back of the trunk mat and reinstall. That way there’s no sticky on the paint and if you don’t like it buy another mat. No harm no foul.

Back in the early 70s, I started putting newspaper between the trunk mat and the floor of my '67 Valiant. Main goal was to absorb condensation and water leaks trapped between the mat and the trunk floor, but had the fringe benefit of sound deadening. I've done this with every one of my Mopars since. Baby Blue was the sole exception, the first time I owned the car. My friend Bob had replaced the factory mat with jute carpet backing that breathed, unlike the factory mat. The trunk floor survived in perfect condition. When I got the GTX back in 2013, the jute had been replaced with an original style mat. I put newspaper under it as soon as I got home.

 

[fesser]

Eldubb440 uses a product called Lizard Skin. After seeing his uses of it I became intrigued and went to their website to learn more. I am going to try their sound deadener and their heat shield products on my car as soon as I rob a couple of liquor stores to get the needed funds. I think he shows examples of different uses in the "A little off the back and sides" thread but I don't have time to search for it now.