Thanks for the quick response

Yeah i don't believe in not changing the ATF and ATF Filter for automatic transmissions as i think they should be serviced regularly. I did change the Filter and the ATF when put the transmission back together. I used ATF Dextron 3.
I don't believe this issue is from the transmission itself mechanically. It could be from a sensor or solenoid withing the valve body but i'm not sure. Unless it's some other sensor or something else entirely. i have no idea.
The computer does not seem to be giving any codes now so i don't know where to start...