Fast06Z06

Lately I have noticed if I run the car hard a couple times and get everything warmed up I hear an annoying vibration and almost like resonating sound coming from the back at low speed take offs and certain rpms. It definately has something to do with expansion. Once the exhaust/ mufflers get hot and expand some something is either hitting or resonating between two metals. I have Kooks 1 7/8 headers, 3 x 3 catted x pipe and stock mufflers modded. Sounds to me like its in the far rear. Im gonna jack it up over the next couple days and check out what I see under there and see if there are any signs of rubbing. But when i originally installed it I double triple checked everything to make sure there where no issues. My gut is telling me it has to do with one of two things. Either the clamp on the midpipe that I turned to the side to keep it high before tightening is hitting the side of the tunnel or its something inside the mufflers.

nutrientcobra

I have a Zo6 I just bought and notice this as well. I was thinking exaust again because I had a C6 that did this and it was one mounting bolt on the back. But now I am thinking I have a brake rattling. When I get the sound to happen, if I hold the break slightly and keep accelerating, it will quit. It is driving me nuts thoe!

Fast06Z06

Mine seems to be related to heat though. Meaning something is not hitting when cold, then expands and is close enough to vibrate against something. Its driving me nuts also. Ill let you know what I find later this week when I get it lifted up.

GasmanZR1

I think that I might have the same problem on my new bone stock '09 Z. No sound when cold, but after warming up I get a whine that happens from 2000 to 3000 RPM if I give it 1/4 throttle or more. It sounds to me like it is coming from the drive tunnel, my wife in the passenger seat thinks it is coming from the rear. I haven't taken it in yet, as I can almost guarantee that they won't be able to reproduce the problem.

AAMC6

Test drove an 09 with this sound. Passed on this car, but was told later that the problem was found to be related to the butterfly valves in the exhaust. it was fixed.

Test drove another Z and purchased it - no sound/vibration. On the ride home (the car now fully warmed). , I heard it Argh! Anyway, I installed my mild2wild switch , turned it off and on a few times and voila....haven't heard the sound since.

My SWAG is that both cars had been sitting on the lot for months and perhaps the valves were somehow sticking trying to open as RPM increased, creating the sound/vibration. I'm just glad it seems to be gone.

TonyC

Hi from acros the Pond,
I had a similar noise and found that one of the rear silencers was mounted too far back.
As everything expanded so the box touched a bolt on part of the rear chaassis frame.
We loosened off the silencer clamps and moved it forwards and now the problem has gone.
I hope this helps.

WFO

Sounds from the exhaust for me were a squeaking sound that drove me crazy. So I sprayed silicone all over the spring hangers and it stopped for good. Each time I'm under there, it gets a shot of silicone spray justy to make sure.

Fast06Z06

Rear Silencer clamps?? Am I missing something here you mean rubber exhaust hangers?

Fast06Z06

Interesting the thing is I leave my valves open like 90 percent of the time so wouldnt that mean its not that if they are fully open?

AAMC6

Agree. If your butterflies are already open and you hear the noise, then I would say that isn't it. On the 2 cars I've heard the noise, both exhausts were stock. Wouldn't hurt to check them out for potential vibration source.

jschindler

Mine does it as well. It did not do it new, but started at about 3,000 miles.

Fast06Z06

True Atleast I feel better Im not the only one. Ill figure it out and hopefully help us all out

qualitycare

Same issue with my '09. I've only noticed it a few times but every time has been after the car is good and hot. I was holding off on the muffler mod in case I needed to have something replaced first but it appears that this is not an uncommon quirk.

Fast06Z06

Tommorow is supposed to be like 55 here so I plan on pulling the car out of the garage and centering it back in so I can jack it up. Ill let you know what I find if anything at all.

Fast06Z06

So I took a look today, not very happy with the results. I jacked it up in my garage and looked over everything. Couldnt find anything rubbing at all. I mean nothing. No signs. Shook the exhaust tapped it with a rubber mallet to find resonance. nothing. I wasnt satisfied there and couldnt see real good on jack stands. So i decided to take a ride down to the local GM dealer that has done warantee work and other stuff for me before. He knows corvettes like the back of his hand

Keep in mind the car wont make the noise until it gets good and hot. Makes two different noises. both at low low speed like just after leaving from a stop. One noise is a resonance at higher rpm like a tiny metal sound vibrating and the other to me sounds like a driveline noise. Well I took him for a ride and did a couple spirited throttle runs to get it hot on the highway and came to a stop and got it to do it. He heard it and said definately something vibrating in the tunnel.

Get it on the lift he double checks everything. Retorques the bolts on the rear cradle that he took down last time to do the axle and check the diff and they check out perfect. So he was stumped. He couldnt find anything either after like 20 minutes basically gave up for now.

He wants me to come back and well hook up his "sound machines" that detect the hertz levels off materials so we can pin point were the noise is coming from and then narrown it down from there. MY gut feeling and the noise its making is telling me its in the far rear not the tunnel and it is something to do with the rear diff or rear driveline assembly. I noticed it also happens when i apply a pretty substantial load at low rpms and make the suspension squat. Almost sounds to me like a cv joint is bad or something rubs when the car squats. Back in my old car when I snapped the motor mount a few times the driveshaft would rub the floor when i hit it hard. Sounds similar but to a much less extent. Im totally stumped at the moment and its driving me crazy because I was planning on taking it to the track soon. The "stealership" gets 99 per hour but thats probably the route I will take because I have no other options and I cant seem to pin point it just yet. I am going to try and look a a few more things and do a few more things to duplicate it to see if I can nail it. Otherwise its off the the stealership for a unknown amount this sucks and things like this will drive me crazy thinking about it all nite long until I solve it.

Carnac

I've had some problems with exhaust buzz that is coming from the forward flange (between the H pipe and manifolds). Started when I put a thicker insulated tunnel plate on. It was very bad, so I put the OEM tunnel plate on, but I'm still get some contact under load. Pretty easy to check out -- take a look at the tunnel plate above the forward flange - if there is contact you will see where it was rubbing. I think I'll have to grind down the flange a bit to fix. The Z06 has very little clearance due to the 3" pipes. Cheers - Jim

Fast06Z06

Unforunately its not that on my car its at the far rear. I took another hour last nite and drover the car to get it hot and try to really pinpoint the noise by myself. IT is definately coming from right behing the drivers seat above the right wheel. It almosts acts like the tranny mount is busted and letting the tranny lift or engine mount is busted letting the exhaust lift and contact something under some load. I looked at everything last nite again still found no signs of rubbing. I checked the axle joints too... nothing. Only found one thing. Fixed it and it still makes the noise. A brake line was rest against the side of the rear subframe, somehow it got bent in just a hair. So i bent it back away but didnt help. Im gonna keep digging and Im sure ill find it. But its DEFINATELY a noise between above the the tire and rear license plate. I also looked at the gas filler tube its coiled in metal to see if it was vibrating above the floor. It had two isolators so doesnt seem to be that either.....

Dr.Ron

I have a similar sound on my 09 Z. It hapens after the car is at oerating temps. It is coming from the right side, very rear. It happensat around 3000 rpm's only & goes away shortly after. Sounds like some thin metal vibrating....It ALMOST resembles a scaled down version of a ricer's exhaust.... It's definately metal to metal contact. I will check it out tonight or tomorrow on jackstands....

Ron

beden1

I have it on my '09 ZO6 too. I think it's definitely something in the exhaust. It sounds like the exhaust pipes themselves are causing the disturbance, or it's in the mufflers? I hear it enough while driving to think it's not in the way back portion of the exhaust, like the tail pipes or the exhaust flaps.

I looked underneath to see if the pipes or mufflers were rubbing anywhere, but could not see anything. My noise actually doesn't sound that bad though, and kind of makes the sound of the exhaust while driving better in a way. At least it's not back firing on down shifts like my C5 did after I installed the Corsa cat-back and AR headers.

I'm having the mild-to-wild installed next week , so I'll see if anything changes.

Did they change the exhaust system manufacturer in '09 by any chance?

TonyC

No, I dont mean the rubber exhaust hangers, I am referring to the joint between the back boxes and the "X" pipe. On my car to move the back box forward away from the cross member it was necessary to loosen the clamps on these joints. I have LG Headers and X pipe with race cats, maybe mine was getting hotter but the expansion for the back box to touch the bolt on the cross member was quite considerable.
All I know is it cured the problem I had