Automatic transmission shifting issue, codes P0443 and P0720

When i accelerate the transmission does not shift gears past 20 MPH. The speedometer keeps moving on its own. The check engine light and the ABS light are both on. When i read for codes i got P0443 and P0720. in the beginning i changes the transmission filter and fluid. it seemed to work for two days then back again. then i changed the vapor canister surge valve solenoid and the output speed sensor. After the code P0720 came off however the truck still did the same thing. I changed the speed sensor but also the wiring and connector again along with the ABS wheel speed sensor. Nothing then i changed the PCM all together. When i did the code P0720 returned. Yet still no change. Any idea what and how to fix the problem. I was told it can't be the transmission because it does in fact shift but does not go past 20 MPH.