I have a 96 beretta z26 with a 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

 

Replace the transmission

 

When checking transmissoin oil, your car has to be running and you have to shift through all the gears first before checking (reverse, neutral, D, 1, 2, ...). Also , your car has to be euhm (how do you call that when the air bubble is in the middle of the waterthingie? ).

Its very important to check if there is still enough (but not too much) ATF (II) oil in your transmission. Those transmissions work on pressure which is provided by the oil. so if there is not enough oil in the transmission, then it cant make enough pressure. And if there s too much oil, then there's too much pressure. So its not a matter of "its over full". You have to get the right amount in it.

If the amount of ATF oil is good , then it will probably be a small valve problem. Hate to tell you, but you wont be able to fix it yourself. (unless you are really really handy ) But its not that expensive.