I wasn't sure where else to post this. I figured either here or in stereo and electronics.

I'm sure all 4th gen f-bodies are insulated the same way mine is.......insulation going all the way to the hatchback, ending a little past the seats right above the fuel tank. The remainder is just covered in thin carpet with no insulation underneath. I'm sure anyone who got stuck in the rain can hear how audible the water splashing in the wheel well is. There's 0 sound proofing. I'm not embarrassed to say that my aging ears are not as tough as they used to be. From what I could tell, most of the car has insulation (under the carpet at least). I figured sound proofing the trunk will make a huge difference for minimum effort (I was wrong, it was a bit more tedious than i estimated) and investment.

So I found some dynaplate on ebay from a guy who was selling a 3 pack which I don't recommend. At the usual price of $150 per 15 square feet, it is way too expensive. In addition to the price, it is difficult to form and bend into tight spots and bizarre sheetmetal shapes, but doable. Finally, I cut my fingers like crazy on some of those sheets. The only benefit as far as I know is that it is extremely lightweight. The only reason I bought it is he was willing to let 3 packs of 15 square feet (45 total) go for 200 so I pulled the trigger. It was obviously a project the guy never got around to and I was afraid the adhesive after a few years may have lost its potency, but luckily it was super sticky. I bought some boommat tape and 12 square feet ofdynamat superlite for the difficult to reach/form parts. The wheel wells and fenders was a huge pain in the neck. I bought dynamat superlite instead of the normal thickness just because I figured it would be easier to mold and fit under the carpet and get into hard to reach places and corners. The normal dynamat would have probably been almost as easy to work with. I did not get the superlite to save weight.

Results:
Better than expected. I had the expectation that it would knock down the road noise half a step and if I was lucky maybe the exhaust. I would say it knocked it down a step and a half. At least. The road noise is noticeably less even with the t-tops off and I was shocked at how it made the exhaust seem to reverberate a little bit less in the cabin. I was very pleasantly surprised that I would notice a difference with the t-tops off! The most shocking part, however, is that I hear less rattling. Of course, this all could be a placebo effect, as I didn't buy decibel meter to do a before and after test. But I'm 100% certain it worked since my expectations were roughly half of what I've noticed. The stereo and music is even nicer to listen to.

I used up 30 square feet of dynaplate, doubling it up on the easy to attach surfaces right above the fuel tank, mufflers, and where the t-tops would go into. I ended up using almost all the dynamat superlite and all of the boommat tape. I got almost all the bare metal surfaces. I have 15 square feet of dynaplate left over that I haven't figured what I'll do with. Maybe I'll do my doors.

My recommendation? If you're going to soundproof it like I did, just get dynamat or some boom mat. I'm sure some boom mat will make almost as much difference as I got using the dynaplate and dynamat. Oh, and the boommat tape is awesome. Really came in handy.

 

I used the boom mat in mine and it really made a big difference as well. For me it was dumped SE exhaust no cats and TSP headers that made it super loud in cockpit. I also suggest using thick spray in bed liner in rear wheel wells. For me doing the inside of doors also helped tremendously.

 

I should've done boom mat. I'm sure I would've gotten similar results for less hassle and cost.

 

I definitely should do the doors. Out of curiosity, would you say you noticed a bigger improvement by insulating the trunk or doors? And what did you do with that moisture barrier? Still use it and put it over the boom mat?

I am more shocked thinking about how much road noise went away WITH THE T-TOPS OFF!!!! T-tops on, of course, is a bigger difference before and after insulation. But, I was expecting no difference with them off. I don't know if you noticed this as well. That is, if you do have t-tops and you ever drive with them off.

 

I think mine was so drastic because I had the dumped exhaust/ good sized cam. But the hole car seemed to sound more solid. And no just threw the plastic liner away, you just have to be careful and use a Razer blade to trim out all door skin pin holes so all factory clips (snap) into place. This is also a great time to replace the felt / metal guides that reinforce the up/down function on the door glass. And if you have a bad window moter now is the time to do it. I nocked out like 3 birds with one stone. If you have more sound material pull off back hatch inside trim and apply to the surround then put trim back over it.... For me it calmed down hatch rattle as well...

 

Thanks man. I was thinking about replacing my window motor. I replaced my window motor with a dorman P.O.S. motor from amazon. Since it was dorman i thought it would be semi decent. It sounded like it was broken. I returned and replaced it with another one and same f'ng thing. It sounded so bad I thought I did something stupid during installation so I removed it and tested how the motor worked on a bench. Same sound. At least it works I guess. It brings the window up and down although it sounds like it's skipping gears and about to break at any moment. From the little research, it seems that many people were having the same issues as I was during that year dorman window motors.

Where did you get your window motor from?

As far as you saying the car sounds more solid. I agree. I'm really shocked at how much more solid it seems for whatever reason. Less rattles which I think is just the insulation absorbing sheetmetal flex. At least that's my guess. Even when I drive with the t-tops off, I think the insulation got rid of some vibration/reverberation.

 

I got my window moter from a local guy that had a couple wrecked birds laying around , so not much help on that one. And yes I tried those dorman ones and had same luck with them. Maybe start a new thread on ' best window moter' hopefully there's some better options out there these days.