I have 2002 f-350 7.3 with 136,000 miles. My truck just started the same thing. Shifts right out of first, into second no problem, then I lose momuntum and the RPM goes to 3,000. Then it shifts. I know I am getting some slip. Could it be the tow safe program from superchips? What is this mechanical diode and where is it. Internal or external. Torque converter or tranny just tired?