Pull the pan and check for any debris. If the truck is stock I doubt the tranny is hurt from what your telling us about it. You need to put a scanner on it (not a code reader) and see what codes it has. I betting it has a shift valve hanging and with a new fluid and filter change and maybe clean the valve body you will be good. Fleece performance does do very good work!! I consider Brayden and Chase very good friends and they have helped me a lot on the dragster and a race truck I had. Very good people and honest.