I have a 96 beretta z26 witha 3100 and an auto trans. My wife said when it would shift sometimes it would rev around 4000 rpm and slip into neutral. When she let off the accelerator it would shift. Seemed mainly from 1st to 2nd. This evening on her way home it quit all together, wouldn't move. Checked the fluid was over full (as is card was in park, motor off) fluid looked a little dirty but not terribly abnormal color. It will not move in any gear FWD or RVS (but park holds). Also the check engine light was on, checked codes and got a P1870, which I thing has to do with the slipping problem. Does anyone have any ideas of where to begin

 

Check the tranny fluid again. Look for tiny silver shavings. Or is it just really dirty. If it has shavings it's done. If not it could just be a valve body. Have you had a flush done to it or anything recently? Or a fluid change?