Sound deadening

[CFster]

Looking to install some sound deadening material in the back of the GTO. Since I switched to hidden tail pipes the "drone" is increased.

I'm thinking of doing the trunk in Dynamat, along with a partition behind the rear seat. I understand Dynamat is primarily a heat and vibration blocker. I should install something on top of it yes?

What are your recommendations? I've seen a bunch of posts about Damplifier, but it appears the site is down and the owner hasn't visited this site since the beginning of last year.

Thanks,
-Colin

[Bryce]

I am very weight conscious when it comes to my car so I would hate to add 100 pounds of deadener.

I have looked into the lizard skin stuff. It sprays on and weighs in at under 10 pounds. But if you sprayed the underbody it would be a rough coat. But you can paint over it.

[Doodler]

+1 for Lizard skin. I'll be using that when the time comes. They have a heat spray and a sound spray FYI

[DJ Mabe]

I'm in the middle of researching this right now. My car is done so spraying it down it's not really an option. I am pulling out some of my interior to do a stereo install so laying down some material on the inside panels is the route I'm taking. I've found a pretty good read on a stereo site that you may find helpful. A lot of our problems come from exhaust so controlling panels from rattling is more critical in canceling out the noise for us than anything else. Take a look at this link and you'll find some type of a solution.

http://www.sounddeadenershowdown.com/cgi-bin/index.cgi

[rohrt]

I didn't find any benefit with adding sound deadner to help with the exhaust drone.

[TT302Z28]

Loose mounts or body contact with the exhaust system?

[GrabberGT]

Im in the middle of adding a firewall behind my rear seat. Im adding fatmat to it as well as the package tray to seal off the trunk. Before was 60-65 dB. I'll post the results tomorrow.

[DJ Mabe]

From the guys that I know that have done this most say you really have to do the whole car to see the benefit. Let us know what improvements you see from doing just the trunk area. I would be curious to see how that helps.

[GrabberGT]

Alright results are in. Took me an extra day because some idiot drilled thru the trunk floor and found the brake lines.

ambient noise is 33dB
with just fuel pump and cooling fan running 54dB
with car at idle 58dB

Mostly it seamed to take the edge off the sound. It just doesnt SOUND as noisy as before.

[DJ Mabe]

That seems like it was well worth it. I wouldn't have thought you would have been able to notice it since you only did the back half of the car. The doors and front floor boards are a must from what I've read. I can't wait to get my car torn apart so that I can get this done. I'm hoping it will help cut down on some of the outside noise.

[GrabberGT]

Let me clarify. I did not do the trunk floors. The entire cabin including the package shelf is done. I have not dont the doors or fender skins either. I might go ahead and do the trunk floor. Im not sure doing more will be worth it. At cruising speeds, its mostly the wind and road noise now. Might be time to shave the drip rails and find those dreaded rattles and squeaks.