I've read several articles and threads but none exactly match the current situation. My son has a 2002 ZX2 that the tranny crapped out in. He replaced it with one from a salvage vehicle. (once he figured out not all transmissions fit!) After he put it in, it seemed to work fine, for about 2 weeks driving back and forth to work. Then, on the way home, it won't shift out of 2nd gear into 3rd. It goes from 1st to 2nd, back to 1st at reasonable RPM/Speeds. Speedometer works fine (speed sensor?) Neither of us know much about transmissions, so reaching out for some help in diagnosing the probable root cause. If it's not something relatively simple/cheap he'll have to return it to the salvage yard for another one (and go through that again). Any help/ideas?? Also, how does he know exactly what transmission he has? He says there are no numbers anywhere that he can find and the sticker is worn off.