2002 Ford F-150 tranny problem

The place to start is by having the diagnostic fault codes read and recorded. Many auto parts stores will do that for you for free, but please understand that fault codes never say to replace parts or that they're bad. They only indicate the circuit or system that needs further diagnosis, or the unacceptable operating condition. About half of the time when a part is referenced in a fault code, it is actually the cause of that code about half of the time. First you must eliminate things like corroded or stretched connector pins, cut or grounded wires, and things like that.