I do what jaydog said if you just want to change the antifreeze. Personally Id remove the upper rad hose from the rad and the lower rad hose from the rad or motor. Drain the antifreeze then use a garden hose and run water throught the block rad, and overflow jug. Then connect hoses fill with water and start truck. Let run till thermostat opens then do over again. After that you could use green or orange antifreeze. The orange is known to eat aluminum so getting all the old stuff out will go a long way
