dirving 45 to 50 mph the transmission shifts into overdrive. Then it will studer. Locking and unlocking till one I speed up, or turn off over drive. Any help with this problem would be appreciated

 

That's a symptom of worn out trans fluid. Change all of the fluid, including the fluid in the torque converter. The fluid exchange (or flush method) is a good way to do it.

 

I agree, I just had a similar problem that turned out to be a rear end problem. I had a vibration that increased at that speed. When I started asking questions and was one click away from a new torque converter, I was told to simply change the fluid. This came from a seasoned Ford Tech. Again, my problem is actually a rear carrier bearing issue, but the advice I got prior to actually locating the rear problem was solid. This guy told me that this is common that they always just changed the "fatigued" fluid and the problem went away. He also suggested a complete drain-out including draining the coverter. What initially made me think I had a lock-problem was a Google search that lead to a TSB that seemed to specifically address noise and vibration at that speed. The TSB only referred to the problem occurring with diesels.