2004 F-250 4WD 5.4L gas engine auto. trans. The trans. has been acting strange. I will going down the road steady rpm and then it feels like the trans. is wanting to go to another gear. And there is a humming sound coming from the engine compartment or maybe behind the dash. That happens intermittently and it strange. I also noticed the power steering fluid bubbling in the reservoir. I never noticed that before but I dont think it is supposed to do that. Any ideas?