Transmission grinding noise

I had a problem with my iac and the rpm was way too high. When I put the gear in the car would jump causing it to damage my transmission. I replaced my iac motor and the rpm is back to normal but now I hear very loud grinding or rattling noise from my transmission, the sound goes away when the second gear kicks in but as soon as it returns to first gear the oise comes back. Do I need a new transmission or is this repairable?