I have a 2010 F250 with 17,000 miles and 100% stock. I took my first long trip this past weekend with no problems at all. I did notice something new going on though. On part of my trip the speed limit goes up to 75 mph. My lane was about to run out and I was trying to get ahead of slower traffic so I put the pedal to the floor. The truck started to shutter and shake but it was still gaining speed. No smoke or anything. I stopped at the next rest area and when I was getting back out in to traffic it pulled just fine up to 80 mph before I let off. It seems that if I am traveling at 70 mph and put the pedal to the floor and it down shifts, this is the only time it will do this. I can be running at 60 mph and put it to the floor and it pulls just fine. Anyone have any thoughts on this? I guess this was the first time I have put it to the floor at this high of a speed.