Meant to post this in 3rd gen 5.9 section. Think it would apply to 6.7 owners also.
Thought Iíd throw in my 2 cents worth.
Long before I found the R&D 3rd gen post from Mishimoto, I had already added two aftermarket trans cooler. Based off of my endless searches and reading, I purchased an Derale cooler with a fan and mounted under the truck similar to what other Ram owners are doing. I had also replaced the front OEM cooler with a Derale unit also. The front cooler was roughly half the size of OEM, but I ran with it any way. During that time, I purchased and installed an Edge Insight monitor with trans temp displayed. Not knowing any better, I thought the broad temp swings from 140 with low 40 degree ambient to 212 stuck in stop-n-go traffic with low 90 ambient temps were normal. That all changed when I finally got around to installing the Mishimoto cooler. On the coolers first run, I hooked up to a 22ft car trailer with an non running F-150 strapped to it. Also, as a way to move said broke down Ford, in the bed of my truck was a 4x4 Polaris ATV. The highest trans temp I saw was 171 in stop-n-go traffic and once up to cruising speed (65 to 70ish) the trans temp was down in the low to mid 130ís. The ambient temperature that day was in the low 80ís. With the Mishimoto up front and Derale down below, my temps dropped on average 40 degrees +/-. Mishimoto did a heck of a job with this cooler and am darn glad itís there.