93 dodge shadow ES 3.0 V6 - wont shift up from 2nd gear

I'm kind of stumped about what has happened to my dodge shadow and was wondering if anyone has any ideas as to what might be wrong. I was driving along and eventually noticed the engine revving high while driving around in town and gathered that i was stuck in 3 or L. Tranny and engine sound fine, no grinding noises (gears) and the transmission has never slipped (sign of low oil/ or tranny is about to go). I pulled off the road checked the trans oil, it was full and clear red with no burnt smell to it. Reverse works well and smooth. Car shifts smoothly from Park to Reverse to Neutral to Drive (Overdrive, 3, L ). Once i go to overdrive, 3, or L, it stays in L (Low). The obvious conclusion is my tranny went by-by. Or is it something else , like a shifting chip (computer) somewhere? Anyone have any ideas before i take it to a shop to get raped?

Your transmission is in something called "limp mode" where the transmission has detected an electrical fault within it and has shut down all other electronic functions until you get it fixed. Go to any shop and have them put the transmission control module on a scanner and see what the problem is.