Whoda thunk it!

[Jay_B]

Hi,
I have a 6.0 L Diesel and hear the same winding down noising after turning the truck off. I believe that the fan clutch has some drag even when not engaged and so while the engine in turning the fan free-wheels but is still turning. When the engine is turned off is stops roughly instantly, while the mass of the fan and clutch keep the fan turning for a few moments longer making the noise. I haven't checked this but I did hear the noise you describe and accounted for it like that. I may open the hood before shutting down and have a listen. It could also be the Turbo (s in your case), they will also still be turning at idle, but I think the impeller/turbine inertia (due to small diameter mostly) would be too low to keep them turning for long. Either way I wouldn't be too concerned.
The dealer can check anyway, that is their job, and they should be familiar with it if others have had bad fans or heard the noise.

Jay.

 

[Peteandsharon]

Thanks guys. I've definitely gone around a lot on this issue and gotten a lot of opinions. The good thing is that knowing what it probably is (whether fan or turbo) makes it seem a lot less ominous. Now i hear it and say "yup, that's the turbo" and I don't give it a second thought. So, I'm gonnna let it go for now. If it gets louder or changes in any way then I can always pursue it. Enough people have a similar sound to make me think it is perfectly normal. Thanks again.
Pete