I have a 2001 4 x4 Durango 4.7 . I have replaced the water pump and thermostat and flushed the system I have good heat sitting still going down the road the heat gradually goes away I have burped it several times once sitting on ramps the second time I backed it down in a ditch to really put it a pitch still no good heat wtf any help to fix it

 

How is the blend door on the heater box controlled on your 'rango? If it has the little stepper motor under the heater box, it's possible the couple (interposer.....) has broken, and lets the blend door flop around.....

 

Would that make it blow warm air out of the vent by the window and cool air by the radio

 

Maybe......