96 3.5 auto stick limp mode

As the title says. 3.5 with auto stick about 160,XXX miles on it. I pulled onto the interstate ramp and was accelerating but it felt like it was not pulling or sluggish to preform so I stepped into it a little more and then weeeeeee. Free rev to red line. Pulled to shoulder and coasted till it dropped to 2nd and went to limp mode.

If I went to neutral killed and restarted the engine it acted fine till it got to 3rd gear and would free rev and go back to 2nd when it slowed down enough..

I got off at the next ramp and checked the fluid. IT's clean, full and does not smell burnt.

I did replace a little $5 relay to the trans, but that is it and did not help.

Pulled codes and found some for a misfire, egr flow, and IAC motor but nothing for the trans.

Do you have to plug into the tcm to get the tranny codes or just the standard obdII connector ??

Any clue what could be the problem? Speedo still still works. Auto stick wont move it from 2 nd unless I cut the car off an then it will let me shift it manually to 3rd where it free revs and goes back to limp mode. I also pulled the battery cable to reset it all.

Really need this thing up and going in a hurry.

Here's the deal. Don't trust parts store scanners. Took it to BJ's and got a 2 codes. 3rd gear is shot. 12 mth 12,000 mile warranty on a used tranny with 90,000 miles on it for $650 and another $500 to install. I could put it in myself if I had the time. I think I'm going to drive my brothers worn out Sundance till I make up my mind what I want to do with it. I may just let BJ fix it in the long run. He's done my tranny work for years, where I pull it and he builds it.

Hard to believe it's shot. The fluid is clean and not burnt. IT was owned by an old lady before I got it. I have babied the crap out of it to get the 28 mpg cause I drive 90miles round trip a day for work. I need to tear one of these apart for myself and see what's in it. I have beat the shoot out of 727's and tore up 904's cause they would not take the hp I put behind them. And now I baby one and it craps out on me.