Transmission issue is my 2008 Durango SLT won't shift into 3rd or 4th gear. I read the code and it came up with the 3rd shift solenoid was bad so I replaces the valve body (updated one) with all new solenoids, fluid (Lucas), both filters and pan gasket. I bought the truck with this problem and the person before me replaced the transmission with a used one and the the torque converter also. It was doing the same thing before he replaced it. The newest thing someone told me is it could be the PCM/TCM as the problem? Does anyone else have the same problem or any ideas? Thank you

P.S. took to dealership and there are no updates for the transmission also.