Aux Trans Cooler-3rd Gen trans overheating

Out yesterday. Temp 37 degrees. Running dirt road in 4Hi 20-30MPH. Climbed 800 Feet over 2 Miles. When I hit the top of the ridge, trans temp almost maxed out. Stopped and put in in 4 Low for a mile and temps dropped to normal.

Concerning: 4Runner TRD Pro-same run and no change in trans temps. I do have full skid plates underneath perhaps blocking air movement.
Not sure how this is going to hold up with any extended 4HI runs.

Thoughts/Suggestions on additional cooling kits? Normal 2 wheel drive operation note crisp shifts and no issues.

 

This has been brought up before. Slow speed going up incline 4wd HI causing Trans temp to spike. Wonder if it a calibration issue or is the transmission really getting that hot.

https://www.tundras.com/threads/2022-transmission-high-temp-alarm.112726/

 

Similar to the gen 2 Tundras, gen 3 transmissions are closed off to the transmission cooler up front. Meanwhile being warmed to "operating temperature" by engine coolant. Mainly to thin out viscosity of trans fluid for fuel economy and calibrated shift characteristics. Only once at operating temperature does the transmission thermostat open to the cooler.

That being said, the transmission temperatures already have a head start on higher temperatures once subjected to lower speed lugging situations.
Just my theory...

 

Agreed. Clearly see this on the Trans Temp Gauge with cold morning starts. Gauge shows temp increase initially and then once the Thermostat opens, gauge drops showing cooler temp for approximately five minutes again rising to operating temp level.

Concern is the Temp Trans should remain at safe levels while operating within normal driving. My recent Off the road run was certainly easy and not extreme by any definition.

 

Thx. Very concerning. I’ve added coolers to every truck, van and SUV I’ve owned. Guess this one will be no exception. Never want to see a trans over 225°. I’ve got to get poking around on where/how I will install.

 

This happened in my damn driveway reversing up dirt/gravel (short but steep) and I was very concerned.