97 F250 series of interruptions when you step on gas

I have a 97 Ford F250 2 wheel drive, automatic, 351 M. Every so often, we would have a small interruption when you step on the gas, at around 30 miles an hour. Nothing serious. We could take it out of overdrive and it would be fine. We have been trying to find someone to diagnose this issue for a long time but since it wouldn't occur all the time, we couldn't have it fixed. Finally, it happened when I was close to an auto shop. The mechanic told me the tranny needed to be rebuilt. The fluid was black. That being done, the interruptions became worse. It is hard for me to describe these interruptions, but when you step on the gas and get up to between 30 mph to 40 mph, the truck does not maintain a steady speed. It feels more like: R..r...R...r.... Not quite a hiccup, smoother than a hiccup. But still the same miss. It sounds like it is tranny problems. The mechanic rebuilt the tranny again. Nothing. He ran a scope which showed the KAM sensor. He replaced the sensor. Nothing. He replaced it 2 more times because the sensor was getting burned out. Now, he has replaced the pigtail wiring that goes to the KAM sensor along with the sensor. He said it was doing fine. All of a sudden, it was right back at it. Also, and this started after the interruptions and after the tranny rebuild, the truck would shift hard at times. That cause, we think, is from the KAM sensor burning out. If anyone can tell me what else I need to look for, I would appreciate it. The mechanic did say there was corrosion built up where the pigtail was, but now the pigtail is replaced. The scanner, like I said, picked up "KAM" as the only issue in the truck. :confused: