70 LT1 - Can you help ID this whistle/ chirping noise?

[David S.]

Hi All,

We're experiencing a whistle/ chirping nose that we cannot ID. If you get the car (70 LT1 Convert.) going 30+ MPH this noise will come. It does not stop until you're 10 MPH or less. It is not related to RPM's, drivetrain, suspension or weatherstrips as far as we could tell. Frankly it sounds like it's wind driven or air driven (air against the car as we drive?). I've even put the car in neutral and shut it off going 30 MPH it ensure it's not anything vacuum/ mechanical. This noise does not happen when the car is idling in the driveway (even at high revs). We removed the passenger side kick panel and dash. All seems as it should. Vacuumed out the birdcage behind the kick panel (clean, dry, no rust just a leaf or two). I'm guessing it's somewhere under the dash or heater box? Heater core and seals were done a couple years ago.

I've attached a video while I'm driving. You'll hear me accelerate to around 30 MPH and when I back off the gas (around 12 seconds into the video) you'll hear the noise. Any idea what this could be? Needless to say it's driving us nuts.

https://www.youtube.com/watch?v=p7v0-Ac9Abo&feature=youtu.be

Thanks in advance,
Dave

[Billy S.]

Re: 70 LT1 - Can you help ID this whistle/ chirping noise?

Randomn guess incoming... how sure are you that your astro ventilation flaps up front beind the kick panels are fully closed (I see you have the passenger lever nearly all the way forward)? I could imagine a whistle at higher speeds if the door were 99% closed, but not all the way.

[Terry M.]

Re: 70 LT1 - Can you help ID this whistle/ chirping noise?

Hi All,

We're experiencing a whistle/ chirping nose that we cannot ID. If you get the car (70 LT1 Convert.) going 30+ MPH this noise will come. It does not stop until you're 10 MPH or less. It is not related to RPM's, drivetrain, suspension or weatherstrips as far as we could tell. Frankly it sounds like it's wind driven or air driven (air against the car as we drive?). I've even put the car in neutral and shut it off going 30 MPH it ensure it's not anything vacuum/ mechanical. This noise does not happen when the car is idling in the driveway (even at high revs). We removed the passenger side kick panel and dash. All seems as it should. Vacuumed out the birdcage behind the kick panel (clean, dry, no rust just a leaf or two). I'm guessing it's somewhere under the dash or heater box? Heater core and seals were done a couple years ago.

I've attached a video while I'm driving. You'll hear me accelerate to around 30 MPH and when I back off the gas (around 12 seconds into the video) you'll hear the noise. Any idea what this could be? Needless to say it's driving us nuts.

https://www.youtube.com/watch?v=p7v0-Ac9Abo&feature=youtu.be

Thanks in advance,
Dave

Dave

I have a drumming from my C6 when the wind is from the right direction and the speed is just right. Mine is from the outside, around the windshield at 60 to 70 mph. I have used the blue painters tape to cover the junction between the windshield and the trim around it, and have narrowed the noise to a certain area, but I haven't yet figured out the exact source.

The source of wind buffeting can be difficult to find.

I would suggest taping the junction between the windshield and the trim as a means of eliminating some areas.

[David S.]

Re: 70 LT1 - Can you help ID this whistle/ chirping noise?

Randomn guess incoming... how sure are you that your astro ventilation flaps up front beind the kick panels are fully closed (I see you have the passenger lever nearly all the way forward)? I could imagine a whistle at higher speeds if the door were 99% closed, but not all the way.

Thanks Billy, hope you're well. That's the first thing I checked. They seem to be closing. Is there a way to rebuild them with new seals though? I even played with the center dash fan/ vac settings and the problem persists.

Want to come over and help diagnose this one?

Best,
Dave

[David S.]

Re: 70 LT1 - Can you help ID this whistle/ chirping noise?

Dave

I have a drumming from my C6 when the wind is from the right direction and the speed is just right. Mine is from the outside, around the windshield at 60 to 70 mph. I have used the blue painters tape to cover the junction between the windshield and the trim around it, and have narrowed the noise to a certain area, but I haven't yet figured out the exact source.

The source of wind buffeting can be difficult to find.

I would suggest taping the junction between the windshield and the trim as a means of eliminating some areas.

Thanks Terry, good advice. Will try it.

Best,
Dave

[Billy S.]

Re: 70 LT1 - Can you help ID this whistle/ chirping noise?

Thanks Billy, hope you're well. That's the first thing I checked. They seem to be closing. Is there a way to rebuild them with new seals though? I even played with the center dash fan/ vac settings and the problem persists.

Want to come over and help diagnose this one?

Best,
Dave

I'd be happy to, feel free to get in touch -- I think before you go nuts rebuilding, lets do what Terry suggested, but just do it to those vents, seal them purposely with foam and listen for a change.

[Jeff P.]

[Jeff P.]

[Jeff P.]

[Ed H.]

Re: 70 LT1 - Can you help ID this whistle/ chirping noise?

If I understand, once at sufficient speed for the noise to start, putting the car in neutral and shutting off the engine, does not eliminate the noise.

Put it on a lift and 'drive' it up to the the needed indicated speed and see if you hear the noise. If no noise, that would suggest the cause is wind noise. If you do still hear the noise???

[David S.]

Re: 70 LT1 - Can you help ID this whistle/ chirping noise?

If I understand, once at sufficient speed for the noise to start, putting the car in neutral and shutting off the engine, does not eliminate the noise.

Put it on a lift and 'drive' it up to the the needed indicated speed and see if you hear the noise. If no noise, that would suggest the cause is wind noise. If you do still hear the noise???

Ed,

That's on the list but haven't been able to do it yet.

Best,
Dave

[Paul D.]

Re: 70 LT1 - Can you help ID this whistle/ chirping noise?

Dave, please use EXTREME CAUTION when performing this "test". Trying to bring drivetrain up to road speed with rear wheels hanging would not be advised by me. Most IRS will "bind up" when rear suspension is allowed to hang unsupported. I have done this before by raising rear and supporting suspension with jack stands under rear shock mounts which will bring half shafts close to normal position. Chip.

[Gary R.]

Re: 70 LT1 - Can you help ID this whistle/ chirping noise?

Dave, please use EXTREME CAUTION when performing this "test". Trying to bring drivetrain up to road speed with rear wheels hanging would not be advised by me. Most IRS will "bind up" when rear suspension is allowed to hang unsupported. I have done this before by raising rear and supporting suspension with jack stands under rear shock mounts which will bring half shafts close to normal position. Chip.

Paul is 100% correct if you let the 1/2 shaft hang and engage forward gear you are asking for a problem. Binding or breaking u-joints is one thing but I know of a nice 73 that broke the posi case doing this.

[David S.]

Re: 70 LT1 - Can you help ID this whistle/ chirping noise?

Dave, please use EXTREME CAUTION when performing this "test". Trying to bring drivetrain up to road speed with rear wheels hanging would not be advised by me. Most IRS will "bind up" when rear suspension is allowed to hang unsupported. I have done this before by raising rear and supporting suspension with jack stands under rear shock mounts which will bring half shafts close to normal position. Chip.

Paul is 100% correct if you let the 1/2 shaft hang and engage forward gear you are asking for a problem. Binding or breaking u-joints is one thing but I know of a nice 73 that broke the posi case doing this.

No doubt gents. I was thinking the same.

It's on the list not completed yet as my NHRA certified mechanic will be doing it.

Best,
Dave

[Ed H.]

Re: 70 LT1 - Can you help ID this whistle/ chirping noise?

My bad. I thought that understood. Apologies.