On cruise control at 75 MPH the engine would occasionally gain about 200 RPM for a few seconds then return to normal. The local Ford dealer diagnosed burnt clutches and other problems and installed a "black box" transmission, which uses none of the old internal or external components. On the way home the truck did the same thing and has been back at the dealer for three days and counting and they seem to be unable to find the problem.
My guess was a torque converter or computer problem but that was eliminated with the new transmission which has both.
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