I have just recently picked up a new 06 CTD. . .unlike my 98 and my 03 CDT this one has a secondary noise that comes alive when the turbo starts to pull. Don't have gauges yet but probably in the upper third of the boost. Only from inside, haven't tried from outside, but almost sounds like some type of pressure bleed off or something. . . .Before I take half a day and deal with the poor guys at the dealer I thought I should at least see what you all think.

 

Are you sure it isn't just turbo whistle. I know mine is more pronounced than it was in my 99 and 05.

Could be a loose hose clamp.
Maybe the factory forgot to install the air flow thingys in the air intake before the turbo.

Really don't know, just guessing.

 

Check your air intake hose from the turbo to the intercooler and from the intercooler to the engine. Sounds like a loose clamp, or less likely, a blown hose. Once you get to a certain pressure (boost), it leaks by.

 

Mine has done this from day 1 also. I think that it is the Wastegate Releiving Pressure at the Higher Boost Levels. Once I get a Boost Gauge Installed I will be able to tell better.

 

I have had this since day one and it drove me crazy, but I am with boostjunkie on this. It has to do with the wastegate. I actually clamped the hose going to the gate closed on mine so it wouldn't open and the sound went away. I took the clamp off and never worried about it again.

don't know why your 06 does and 03 didn't but these trucks are strange sometimes. just glad they run so dang good.

 

Electrically Controlled Wastegates are louder for some reason compared to the Manual/Mechanical ones. I have installed many AGP Wastegates and tuned many SRT4's with them and never heard anything like this. I guess that the inside of the New 06's are so quiet that you can hear the small things!! But 30+psi of boost getting bled off should be loud really!!!!

 

Mine does this also...seems to coincide with the turbo spooling up, but is not as high pitched as turbo whine. It is loudest at about 1500 RPM, even in neutral. Mine didn't do it from the begining, just all of a sudden started doing it! I made sure all clamps are tight. My truck goes in to the shop on monday for some little piddely warranty work, I'll have them have a listen.

 

Thanks all for the reply. . .just to clarify almost sounds like a vacum hose is leaking under tha dash. . .right?

 

I wanted to bring this thread back to life. I just recently have begun to hear a "whooshing" sound when the transmission shifts into overdrive. It too sounds like an air leak of some sort. Maybe someone can shed some light on what it is.