HELP... Please



On the way to work today everything was fine (about a 30 min trip) once I arrived at work I stopped at a stop sign when I went to take off NOTHING 3000rpm and about 2mph, so I dropped it into third and the car went as advetised and shifted fine. While driving in 3rd I put the shifter back in OD and the trans started to slip, I pulled over to ck the fluid and TV cable all OK I went to back up and again 3000rpm about 3mph in reverse.

I don't know if this matters but on Sat I put in a 2800 stall converter. The car was fine until today.

Thanks for your help in advance. If I need to ck something let me know where it is and how to get at it as I am not a transmission expert.
More Info

I was driving home and it was still doing the same thing so while driving around 55mph in third I shifted into 4th the RPM's went up for about 3 sec and then a clunk and I was in OD the lock up worken normal. When I got home and stopped for a light it was back to my original problem.

odd that when OR clutch isnt on it wont move. OR sprag might be hurt. in 3rd, all is normal?

Man.... let me think about it.

I want to ck on something in the morning. If you give me a call in afternoon I will have an answer. I want to trace something I can't do here. I think I know whats going on, but I want to be sure.