1989 Toyota Camry transmission replacement

I pulled out the old transmission and installed a used one from pick n pull. I used the torque converter on the replacement tranny. Everything went back together fine. Upon starting the engine it started making a continuous grinding noise. I shut down immediately and pulled the starter as that sounded like where the noise was coming from. I checked to make sure the flywheel was moving freely and it was. I reinstalled the starter and tried starting again- with the same results. Shut it down immediately. It sounds like the starter is not disengaging the flywheel on start up. Any ideas or help would be greatly appreciated!