Before assuming that your 5HP24 has a problem theres a couple of things to check. Like Kojack said, you can get spurious messages on the early L322s if the battery voltage is low for any reason. Youd be better getting the codes read on Testbook/T4. If it indicates a transmission output speed or sensor fault then it could be the rotary potentiometer in the transfer box motor thats faulty rather than the transmission. Of course it could also be a transmission problem - the DTCs should give a clue.