Tranny broke?

I have a 1993 Chevy Cheyenne 4.3 4x4 with what I believe is a trans out of a 97 truck. It was installed before I got the truck and I just need some possible ideas of what may have happened. It has always shifted solid and the fluid is bright red,never run hard,by me anyways. I was getting on the interstate to come home,getting up to speed of 65,was at about 55 and just out of no where the engine revved up and the trans just would not move the truck,engine running great and if I revved it up around possible 4 or 5 grand it would slowly crawl along but, I doubt it would have climbed any grades at all.,I coasted to the side of the highway and had to be towed home.
Just before it did this it had a pretty bad vibration if I revved it up a little more than usual. I know the 4.3 is a vibrator or so I have heard and read but, this was more than normally felt though.
Any ideas would be a great help,I am good DIY mechanic but, just need some ideas,,thanks in advance for any help.