I just did mine last month, I loosened the valve on the bottom of the radiator, drained, ran the enging a min with the front and rear heat on to let the water pump move the coolant, I then kept allowing it to drain, I also removed the upper radiator hose and drained that, be sure not to let the coolant get all over the upper intake, coils and plugs. One useful tip is to take off the coolant resiviour (sp) drain and clean that and when it's out I found that the lower hose that goes to the bottom of that tank will fit right onto a garden hose so you can keep the drain on the radiator open, pump wanter into that hose and if the truck is running with the heat on eventually it will be completely flushed. Then drain all the water out and replace with coolant/water mix