i have a 2001 trans am (auto) and a couple of weeks ago the rpm's started jumping to around 3,000 while shifting from 1st/2nd and 2nd/3rd. then the 'service engine soon' light came on the next day. i was due for an oil change and was going to get one that week, so i figured it was from that. afterwards the service light and high rpm's were off and on. i took it over to my mechanic on saturday, but the light disappeared and by dumb luck the shifting was normal. we went on a 10 minute drive and it didn't screw up once. he told me to bring it back monday. same result. warmed it up for 10 minutes, drove it for 20, nothing. i took it out for another hour by myself right after and it happened about 3 or 4 times. the service engine soon light hasn't been up in a while, but the shifting problem is still happening a little. does anyone have any ideas what it might be? advice what to do? i don't want to keep driving, hoping it goes away.. but i don't want to get all paranoid and start dishing out cash for 'hard scans' and such. any help would be much appreciated!

 

you're not gonna get many replies about a 4th gen on a 3rdgen forum. - In fact, the post will probably get locked shortly.

anyhow, your 4l60e is electronically shifted. The computer shifts the trans according to the tps sensor position, the vss(speed) sensor, engine load, which it reads through the maf sensor, and also varies some according to engine temp(cts sensor) - Since you say it does it occassionally and the ses light comes on, I'd say you have a sensor malfunctioning, so try to get it on a scanner while it's acting up/when the light is on.