Whistling/pinging sound in cab of truck?

[Ryan Mikkelsen]

I have an 06 CC, shorty with and SCT Live wire, Studed, and 4" turbo back. When is is cold outside, and I go over 90km/h, there is a whistling/ringing sound that I can hear inside of my cab. I sounds like it is coming from the middle somewhere. As I go faster, the sound gets louder.
The sound seems to be a function of speed rather than engine rpm or boost.
Does anyone have any suggestions as to what it may be?
I am not very mechanically sound, therefore I don't really know what it could be.
Thanks for your input ahead of time.

[outlawdiesel]

is it your lid on your over flow bottle

[Ryan Mikkelsen]

Originally Posted by flyin hawaiian

is it your lid on your over flow bottle

Thanks. Do I just have to tighten it, or buy some aftermarket one to stop the problem?

[BigRobRN]

I got my 06 out of the shop last week for the same thing.
Diagnosis = EGR cooler failure.

Got me a new EGR cooler under warranty along with a new oil cooler. They performed some sorta TSB and repaired a few things while in there.

I was blowing white smoke and whistling too. Ended up being the degas bottle cap.

[Ryan Mikkelsen]

Originally Posted by BigRobRN

I got my 06 out of the shop last week for the same thing.
Diagnosis = EGR cooler failure.

Got me a new EGR cooler under warranty along with a new oil cooler. They performed some sorta TSB and repaired a few things while in there.

I was blowing white smoke and whistling too. Ended up being the degas bottle cap.

I hope that it is not my EGR cooler, I just had the same thing as you done on my truck.
It was not as cold today, and my truck did not do it.?!