Yes, it is possible.

When I lived where it got cold (SE Michigan) I put a piece of cardboard in front of the trans cooler for the winter months.

 

Thanks Mark and all. I think for now I will go ahead and do that flush with Mobil1 while simultaneously replacing my OEM 7.3 cooler. They are terribly expensive, and I’d feel good knowing I had a brand new one as opposed to one over 20 years old.

I am pretty conscious about getting the truck out for a long drive on the cold days to make sure it gets up to operating temp before shutting it off, but I don’t see the need for me to have extra cooling capacity as the truck doesn’t see many severe duty days.

 

I've been pretty happy with the 6.0 cooler and Schaeffer's All-Trans Supreme - after moving to this combo have never seen the gauge get high enough to worry about when towing the 5th wheel.