I have an 03 F150 and I started having similar problems a while back. For a few months, I noticed my truck would kind of "jump" when I was accelerating, but it only did it every once in a while. A few days ago though, I was on the highway trying to speed up and around 50 mph it started shaking pretty bad. I let off, tried to speed up again, and it shook again. So I let someone else drive it and they think it's transmission problems. It didn't shake as bad, but they said it's slipping in 3rd gear. I'm probably going to take it in tomorrow