2003 F150 Supercrew Humming noise
 

Greetings,

I have a 2003 F-150 Lariat Super-crew and it has around 140k miles on it. The past few weeks I am hearing this humming sound kind of like if the abs sytem were to engage when the wheels start slipping on wet roads or something?>>>
But I don't think it's the ABS system. Today I was sitting in the truck with it idling and it also does it then. Well it hummed every couple of minutes or so and I noticed when it did it my rpm gauge went up slightly until it went off (about 5 seconds each time).
I'm completely clueless as to what this is but it doesn't seem to be affecting the truck yet at all other than hearing a humming noise for a few seconds. Any ideas? Thanks ahead of time.

Dave in Texas.

Can you post a video? Like on YouTube and link it here so we can get a better idea of what you are talking about?