I have a 1995 Chevy 2500 pickup with a 5.7 and a 4L80E trans . My problems is I put the shifter into OD and it will shift up to 3rd gear untill I reach 30MPH after 30 it will kick down to first untill I slow back to 30 then it will shift up to 3rd gear. Then I put the shifter in 3 and I can get up to 40mph before it kicks out of 3rd untill I slow down. And then some times it will not shift out of first gear at all after it has sat awhile.I hope you understand what I am saying. If you need more info I will try to make more sense.Thanks for your help P.S The shop I took it to said my ECM was bad and some bad wires, so they put a new one in and I still have the same problem.