My truck started overheating out of nowhere! At Least I think it is. The temp gage will shoot all the way up to the red and once it gets there, it will drop quickly back below 220. I thought it was a thermostat but I changed it and its doing the same thing. Back and fourth with the temp gage. I have No idea what it is. Any ideas? It's just weird that it goes to red and drops so dramatically back to normal. It will do this 5 times in 30 min.

Completely fill the radiator with coolant. Follow Dodge's recommended procedure to fill the cooling system and ensure there's no air in the system. Air in the system can cause sensors to go crazy.