Sound proofing for an overly noisy drivetrain?

[Skant]

I've been dealing with a noisy drive train in my Corvette. At first, I thought it was the 4.11 gear installation, but after driving other vettes with ZF6 trannies, it's clear to me that my drive train has always been abnormally noisy. The 4.11's just made it louder still.

The shop thinks it sounds like sound proofing may be missing from the car. Even opening or closing the little door on the center console (the one that covers the cup holder, etc) makes a significant difference in noise level... implying that there's no sound proofing under there at all.

I've dumped about $10,000 into eliminating this high pitched whine it makes on the freeway (65+ mph). The ZF6 tranny has been replaced three times. The ring and pinion have been replaced twice. None of this has changed the sound I've been trying to eliminate at all. So it seems that messing with the drive train hasn't been the right direction.

Perhaps it is a normal sound that you just don't normally hear.

So maybe sound proofing is missing from the car. But even if it isn't, additional sound proofing could be added.

So my question is... does anyone here know about sound proofing a C4 vette? The particular sound I'm trying to stop is high pitched and seems to come through the center console and rear deck. It's actually not as loud as say the tire road noise... but it's much more annoying in nature. To my limitted understanding of sound proofing, this should be one of the easiest sounds to block.

Searching the archives, I see some reference to using Dynamat Xtreme or Koolmat in the trunks on C5's. Koolmat apparently has products for C3's and C5's.. but not C4's. I can't find much about specific applications of Dynamat.

At this point, I'm pretty depressed for all the money I've spent on the drive line and I still get to listen to this annoying whine. I'm really hoping that sound proofing is a viable answer. I'm running out of hair.

- Skant

 

[67HEAVEN]

I know this won't be any help to you, but I love the whine out of my new Richmond 5-speed. It matches perfectly with the growl out of the Hooker side-mounts and the grunt of the new 502.

I just love all the sounds of this old machine.

 

[Skant]

I like most of the noises this car makes. It's just this one that I find quite irritating. I'm hoping I can knock that down. The rest of the assorted growls, rumbles, whirrs, hisses, and snarls are pleasing.

- Skant

 

[dburgjohn]

I used Dynamat on mine after installing muffler elems. I love the sound outside, but inside it was loud. The dynamat really cut it down. I have heard of people using multiple layers though I used only one. You probally won't get it as quite as a caddy, but you can make it better. Also you might think about a nice cat back exaust system to dround out the trans!

 

[tyrel]

I think it's time you start looking at dynamat or any of its cheaper cousins. You can do this job yourself, although removing every little thing from the interior and installing the stuff will take you about two days if you take your time. This is a job that I'm thinking about doing soon, they sell dynamat on ebay for much less than you can get it anywhere else. It does add weight to the car, I read somewhere about 40 lbs, but I could be wrong. Good luck!

 

[Skant]

dburgjohn: I've got a borla exhaust on her. But the Borla has a very throaty low pitched sound, so it doesn't actually mask the high pitched whine much.

So it really worked well then? I'm imagining that it knocks down high frequencies more than low frequencies... which is exactly what I'd want.

I talked to a guy at a sound place that didn't seem to really understand what I was saying... but he was saying that if it's an airborne sound rather than a metal vibration through the car, the Dynamat may have little effect. And I was thinking maybe it won't work so well then because it's from the pumpkin. But on second thought, the carrier is affixed to the underside of the rear deck, is it not? So maybe the rear deck is indeed a resonant surface for it. Hmm... that would explain why it sounds like it comes from everywhere in the rear.

Hmmm... well, I should think that if it can quell exhaust pipe noise, it should quell drive train noise, too. I'm definately leaning toward giving this option a try.

tyrel: I do race this car, so I hope to not add much weight. It looks like on Dynamat's website they claim their Dynamat Xtreme is half the weight and four times as effective (and twice as expensive)... about half a pount per square foot. They also have some liners that go over it that are supposed to boost the sound proofing quite a lot.

I'd probably just do the rear deck including the rear wheel wheels in the car, I think. I'd guess that's about 16-20 square feet. So theoretically I'd be adding about 8-10 pounds. I'd rather shave off all the weight I can, but realistically this car is used more on the street than the track. And 10 pounds isn't that much. This car will still be lighter than stock after that addition.

- Skant

 

[berky2500]

Skant,

I recently bought a GS with the ZF transmission. My first ride in a car of this type. I drove the car 300 miles the first day to get it home, and by the time I got home, I was kind of concerned about not only the whine from the transmission but the significant heat coming from the tunnel.

One of the first jobs I performed was to gut the interior for cleaning, repairing and insulating. I have used a foam insulation in three vettes now with good results. It is called Frost King Duct Insulation, it is a 1/4" foam insulation with an aluminized backing. It is about $15 a roll at Lowes and it takes three rolls to do an entire car, only two to do the front.

The other thing I found is that the boot around my gearshift was cut out and there was an opening right to the tranny and exhaust. I covered the opening first with a heavy piece of rubber mat and then a layer of dense carpet padding. Finally, I added the Frost King insulation over the entire tunnel.

The result is I can no longer hear the transmission whine over the exhaust, I also have a much cooler interior. I hope this helps. I've watched off and on as you've poured money into your car, and feel for you not being able to enjoy your car the way you should be able to enjoy it.

Shawn