I have a new 2011 F150 Platinum with Eco engine. While going up a mountain highway yesterday. I was following another vehicle and at both 80km and 100km per hour i suddenly heard a noise from the undercarriage. seems to be like the transmission or drive shaft as everyone in truck heard the different sound. As soon as I applied the gas it disappeared but it almost sound like the transmission was disengaging or something like that. No sudden jolts or anything like that just a different sound. Any ideas what it could be and what I should do. I doubt I can make it happen again without being on a hill. No grinding sound and not your standard gear shifting sound almost like something was spinning on its own, really strange.
First time on this site but I have found this helpful with my old 2008 F150. You folks are a good group compared to dealing with some mechanics and such up here in Canada.