My brother in law recently purchased a monticarlo ss and snapped his forward band. He found a jy rebuilt trans for cheap so we gave it a shot. First time I just tossed it in with fresh fluid and it drove good however wouldn't shift into third and I couldn't force it via scan tool so I figured potential shift solenoid. We pulled cover swapped shift solenoids tcc and pressure solenoids and topped off with fresh dex 6. Then it started to shutter on take off so I tried trans adapt resey in snap on scan tool and threw in some shudder fix and a bottle of Lucas. All was fine and stopped shuttering and shifted great yesterday. Now today its like we never reset the trans adapt and it's shuttering bad and won't shift again. I'm starting to think it's a trans controller issue because I noticed these have a separate controller. Any tips would be great. I warned him when he bought it lol