Crossfire

I have a 1995 K2500.It has a rebuilt 4L80E trans and a 5.7 engine. The truck ran fine after the trans was rebuilt, but one day the battery died and after I replaced it there was only reverse and 2nd gear. The only code coming up on the OBD 1 was 85. I reset the computer (neg. cable off 20 mins. the key on for 5 mins) and when I drove the truck to gas station it shifted fine, I had all 4 gears. when I started the truck to come home I was back to 2nd gear only. I changed the ECM and now the truck goes from 1st to O/D in about 10 feet. Is there something Im supposed to do to the ECM to make it work with this transmission? Any replies would be appreciated.