The problem might not even be the transmission. The computer monitors sensors on both the engine and transmission. Some of these sensors, if faulty will cause the computer to command full line pressure from the transmission pressure control solenoid. When at full line, the transmission will shift harsh, this is good and protects the transmission from destroying itself. Where I would start is a scan of the computer for any trouble codes. Like I always say, “Dont condemn the transmission just yet”
transman