If I remember correctly, the Hayden aux ATF cooler "LPD design" does not have built-in temperature flow controls. The Tru-Cool brand does. re: "Tru-Cool self-regulating coolers - it is the oil that regulates the cooler. Thicker oil that is below the ideal operating temperature bypasses the cooler through the upper two plates. When the temperature rises, it becomes thin enough to pass through the entire cooler. TRU-COOL's superior heat transfer is efficient and self-regulating
." statement within the top of http://www.transmissioncoolers.us/Me...ool-coolers-hd
Within my area, winter temps do get down to -35Fs / -40Fs. And if driving 60 mph, "wind chill" can drive its frontal temps down to -50s as well. For some folks in my area, they do NOT winter wrap their aux coolers. My local transmission specialist tells me that "wrapping" the aux ATF cooler (regardless if Hayden, Tru-Cool or Mr Transmission) during winter months is a great "proactive" protection trick. He recommends winter wrapping for all his aux ATF cooler installs. Thus, why I installed the aux ATF cooler in my current mini-van with space gapping - to allow "winter wrapping" ability.
If temps drop down to -20 F (Plus driving wind chill negative influence), I would also recommend "winter wrapping" your vehicle's aux ATF cooler - regardless of its specific aux ATF cooler brand. Simple thick plastic bag around the aux cooler is like a thick winter coat - on those deep freeze winter days.
Hope this "proactive protection" idea helps.