Have a 2007 Ford Explorer V6. What needs to be done if transmission fluid is in the radiator?

 

I would think there is a leak in the cooler line that goes thru the radiator. You could disconnect the transmission line and put the radiator under pressure to check it for leak.

 

FIRST thing: Don't even start it up with this condition. The oil will go into the radiator when under pressure from the trans. Once the engine is off, no more pressure from the trans. But the radiator is under pressure due to the heat and pressurized cooling system. Cracks and leaks work both ways. Coolant in the trans....NNOOOOOOOOo!!!!!

 

In short, replace the radiator flushing the coolant system at the same time, then flush the trans as you dont want to take chances here. I have seen this failure before in radiators.