I have a 2011 Grand Sport Corvette (LS3) with a knocking noise. I just purchased it with 3800 miles. The dealer tried changing out the Torque Converter and checked the torque tube. The video is on YouTube.

http://youtu.be/zwSkS8JPq8U

It's a knocking noise that occurs on occasion and noticeable mostly at idle in Drive or low RPM. It disappears after a while as in the end of the video. It isn't the tick of the injectors and is a knock you hear. You can hear it easily in the car but not from the outside or with the door open. It sounds like it's coming from behind the dash and this video is made with a Blackberry using its video recorder. So the sound is evident to the ear and in fact you can almost feel it. At times it is loud and other times quieter. I even move the phone to the rear and the sound isn't evident.
You can go all day without hearing it but other times will occur several times a day. It's not only on cold starts and can be after the car is warmed up. The car is stock. Any advice? The dealer isn't sure what it is at this point and are thinking of sending the video to GM. I had to capture it on video as it was so intermittent and on test drives it wouldn't occur.

The AC is off as is the radio/CD.

The dealer is suspecting the Torque Tube and has the car again. I will post a response on whether or not this resolves the issue. I hope it isn't a lengthy process for them to obtain parts and repair it. Last time they had the car over a week. I can't understand how a brand new car could have issues with this and only 3800 miles. You would think it was inspected, quality control, etc. on assembly. I bought the car with that many miles maybe it was abused during that time. Who knows.

 

Could it be the fan motor? Turn your ac off & see if it goes away..

 

The AC was off as was the radio. Thanks for the idea though. They also had a thought it was the pump between the gas tanks. Apparently it has two. However the problem occurred when the car had a full tank of gas. I only use 91 octane and from Chevron, Shell or 76.

 

The location of the sound can be deceiving from inside the car. I would have someone else put it in drive so you listen from outside the car. It sounds like something may be loose and ocassionally is rubbing/knocking against something else. Since idle has the most shake it might be just enough. My sense of it is you need to really localize the sound so you know where to look/begin.

 

Have them check the fuel tanks. We had this issue on a 07 ZO6 with a knocking sound. It was sometimes at idle or low speeds and not RPM effected. It ended up that the foam seal that is on the side of the tank was not there and the tank was hitting the car while the car was idling.
good luck.

 

Thank you, I will certainly ask them to check that out.

 

easiest way to locate any difficult sound is with a rubber hose, or a section of garden hose a few feet long. One end to your ear the other end fish through areas you suspect the sound is coming from.

 

I have an update editing the original post. Comments are welcome and appreciated.

 

Has anyone ever tried this Torque Tube Assembly (drive shaft coupler and drive shaft) from Black Dog?
http://blackdogspeedshop.com/index.p...d=41&Itemid=55

 

Dealer replaced the Torque Tube. Seems to have been the issue.