Trans problems

I have an 01 cummins with a built 47rh. Goerend parts. It has a high stall tc , I think the number was 3200. When shifting from park or neutral to drive or reverse the truck bucks then stalls out. I have to pretty much neutral drop it and keep my foot on the throttle for a few seconds then it clears up and shifts fine. I can drive to a stop sign or whatever and stop and it stays running like normal. Only happens when innitially shifting into forward or reverse gears. Talked to goerend when I bought the truck with everything already installed and they said it was because it's a higher stall tc . But it has gotten dramatically worse since then. It also will not shift into overdrive. It runs through the gears up and down just fine just won't hit overdrive. I changed governed pressure sensor and another solenoid and also the filter. Other than that the trans works great. Any help would be awesome. I'm out of ideas.