is overdrive electric shift?
what would cause overdrive to kick out?
this is in a 95 monte carlo

Well a kicking out over drive can be the first sign of the tranny going i had a tranny go about a month after the overdrive would kick out on anything but a nice down hill slope. A couple different things happened the oil somehow ended up low and the torque converter wouldn't work any more so the transmission eventually burned it self up. I would get it to a shop to be looked at. But if you don't i would say pay attention to the transmission if you start noticing other transmission "issues" have it looked at.