Hearing a whistle sound/noise in front of truck. Though it maybe the belt slipping, but has made the sound running down the interstate at 70 mph.

 

Hi there,

While driving on highway, if you depress the gas pedal, does the sound quits?

I remember about a similar problem found on Ford Explorer 2003+ and it was from the catalytic converter. I'm not telling this is your problem because we're talking about two different cars (D's are better ) but at least I have seen two Explorers with this same problem. It was corrected after the part got replaced.

Hope this help.

Regards,