At 30 degrees or colder and between 55 to 70 mph the truck whistles.. Not sure what is causing it but it is annoying.. Any other people notice this..

 

I also have high pitched whistle in cold weather,thanks for replies in advance.

 

Do you have the sirius antenna from the factory on the roof? My 06 does that and the 08 f-350 I had did the same thing and I belive it is the antenna that causes it.

 

i have not experienced this on the fords, but the kenworth i drove for work would do the same thing. it turned out to be the windshield gasket shrinking in the cold, thus leaving a gap between the gasket and the body, resulting in a whistle. i dont know if this is a possibility on the 150, but it could help with the search for the whistle.

 

I have an 08 and it has been whistling since it has gotten cold too

 

I had a whistle on my old truck during the cold temperatures. I kept trying to track it down and finally figured out it was RPM dependent not speed. At the end of it all it turned out to be my alternator. I replaced it and the whistle went away. I almost didn't replaced it because it was working fine, but it finally got to the point where it was really annoying me. Not saying this is your problem but it's worth a look.

 

Had some problem new alt. fixed problem
There used to be a TBS on here about the problem

 

I got a 04 supercab no external antenna's except the am/fm antenna and noticed this the other day at a constant speed, once I dropped a few MPH it went away and haven't heard it since. Thanks for the heads up, I'll pay attention to the atlernator, NEVER would have thought that!