We did Teton Pass with our 2014 Ecoboost pulling 4200lb TT westbound in September. Air temp was 61F and the trans temp as we crested the pass topped out at 226F. I pulled into the big turnout at the top and let things cool down before we began the descent. Using the selectshift and staying in 1st-3rd gear, letting the rpms climb up to 4500 and using the braking technique mentioned earlier works very well on the downslope.
The Eco has more power than necessary for just about anything you would ask it to do, what it lacks is cooling when using that power. We got home from that trip and I installed a larger trans cooler from an Excursion. We'll have to wait for next season to see if it helps.
