Installed a used transmission

I got a used transmission did the change in my truck. Started the truck and there was a grinding noise so I cut it off it was late so I went in. Contacted a few friends that said it sounded like the starter was staying engaged. Next day dropped the starter and a nut I was going to put on the exhaust and had dropped so I used another one because I could not find it. The nut had dropped on the starter and was laid against the bolt where the wire runs from the solenoid to the starter and against the side of the starter. Moved it tested the started did not seem to be working properly so I disconnected it and tested it outside of the truck and it worked the second try. Put it back in started the truck had the same noise but it quieted some so I put in reverse and it caught after a minute then stopped pulling then started back pulling. Exactly the same in drive. After doing some studying I feel one I did not seat the torque converter and two I attached it to the fly wheel before installing any bolts on the bell housing. I even had some trouble getting a couple bolts in but jacked the transmission up and down to align them. Please advise on what I did with the torque converter is my cause or if it is something different. I desperately do not wish to remove the entire transmission and drive back an hour to remove another one and do it all over again. Help!