My 98' Cherokee won't shift from first gear into second until it runs to warm up for a few minutes, after that it shifts fine. The other problem is that the Overdrive went out. It shifts through all of the gears, the converter locks up as it should but it won't go into overdrive. The "Check Engine" light is on and it does show several tranny trouble codes, but where should I start?

Get the codes if you can....it is probably the NSS.

I have already checked and cleaned the Neutral Saftey Switch, didn't fix the problem....

What are the codes?

I will check them again when I get off of work tomorrow. I delliver mail and have a scanner so I will connect it while I'm on the route and see if it pulls any more codes.