I am new to Dodge so please forgive my ignorance! My son has a 78 truck that stays in 4WD all the time. Now it doesn't want to shift into third. I have been trying to find a modulator valve, but no one lists that part for this model which leads me to believe it doesn't have one, or it's called something else. I am totally clueless as to what to do short of taking it to a mechanic, but we enjoy doing these things ourselves when feasible. I'm really hoping some of you guys can give some insight on what to do, thanks for the help!!!

 

is the transfer case a 203 ?

 

Check the wiring where it goes through the floorboards