Transmission cooler and thermostat (OEM and Aftermarket)

[RaleighDiesel]

Hi all!



Joined xoutpost after being in the BMW Diesel group on FB.

I drive a deleted and tuned and lowered and well-maintained 2012 X5d, but I've just recently started regularly monitoring data via BimmerLink despite having the vehicle since June 2019.

I'm seeing trans temperatures creep up to 93 degrees C and I plan to service the transmission (last service was at 95k, currently at 130k) with the ZF FCP kit, but I also want to add an additional transmission cooler. I know there is a factory unit controlled by a thermostat used to bring the transmission up to temp quicker, but is that really necessary when in a warmer climate? Car has a cold weather package (heated seats F/R and steering wheel) and when we lived in Milwaukee, WI, it was great. In Raleigh, NC, i feel like its not as necessary

My question is:
Should I plumb the cooler before the oem trans cooler thermostat or after? Is that thermostat necessary in a warmer climate?

Ideally would like to bring the operating temperature down to 75-80degC range for sanity and longevity's sake. Would like this vehicle to last me until 250k miles (hence the 35k mile trans service interval)