My experience was great with the Hayden cooler and a thermostat and computer fan on it, living in a warm and cool climate in So Cal, pulling hard in mountains and deserts four seasons. It also gave me a good way to purge fluid to all new. It kept the trans (and and as a secondary effect, engine coolant) cooler in hot weather but the engine thermostat prevents over-cooling.
Unfortunately, my beloved '09 2.5i Limited was hit on the driver's side front totaling it, end of that story. Fortunately, I installed the cooler and fan in a well protected area (all else in that area was really smashed) and I removed it at the body shop when they told me I wasn't going to get anything for any of my extras and care. It took about 15 minutes to remove and connect the hoses back to the distorted radiator and clean up my drips. I intended to find another '09 2.5i Limited and tried for many weeks, but no luck in So Cal in the limited time I had. I had to replace the car with a more modern Mazda CX-5 to get a car with a trans that shifts, but can't add a cooler to modern cars like CX-5's because the minuscule built-in coolers have engine coolant routed internally without external trans fluid circulation.
I think this is what is relevant to your question: The CX-5's light-duty internal cooler has the trans running at about 190 degrees+ (normal trans operating temp, give or take a few degrees from a dash mounted OBD gauge) and uses a special very expensive fluid, compared to about 160 degrees or less with the Hayden cooler on the Outback or my Lexus RX300 as measured by the Hayden adjustable fan thermostat setting that only needs to cycle momentarily when the engine coolant stops circulating when I stop the engine (heat soak) or in extremely hot weather in traffic.
