Towing trans tests

I'd say go with the cooler to be on the safe side but I'm just a 2016 owner who never monitors Trans temps

 

I took my truck up to the mountains the other day. It go up to 190 with the torque converter running in the 200s. Normal and safe to me.

 

I have been towing smaller campers for years with my 08 Tacoma, 17 4Runner, 19 Tundra 4.6 (big mistake) and now a 17 Tundra 5.7. I used a ScanGauge2 in all instances. One thing I learned is when your just cruising along in any gear, there is no heat being generated in the transmission. I could drive an hour and have temps stay at 200F or below. The only time when heat is generated is when the torque converter unlocks and the transmission starts to hunt or downshift. It's when the torque converter unlock is when heat spikes.

Personally I use Tow/Haul mode and bump through S4 S5 S6. If I'm on a flat section S6, if in light rolling hills, S5, and heavier climbs, S4 or S3. If I'm in S3, I drop my speed, I'm usually in no rush.

One lesson. On a cross country trip with the 4Runner and a 17' trailer, elevation was the enemy, I couldn't beleive how much power was lost higher up. You lose 3%hp per 1000' of elevation unless you have a Turbo.

 

Real world tests.
Does a Tundra Need a Transmission Cooler? We Put It On the World's Toughest Towing Test to Find Out! - YouTube

 

Who revived this horse we've beaten to death...

 

How are you measuring engine oil temp? Your post implies you are measuring it separate from trans temp.

 

OBD Fusion