Towing trans tests

So i finally did a camping trip with my scanner installed the whole time. Trailer on the scales weighed 4380lbs. Truck had approx 300lbs of cargo in bed. 2010 model with external trans cooler. I used to tow exclusively in S5 and enjoyed amazing fuel mileage of 13-14.


towing in S4- trans temp 203-204 (TC) consistently

towing in s5- trans temp 210-218 (TC)

Both on flat freeway at 65mph.

The extra rpms took 1mpg off the mileage, however im thinking the lower trans temps will be worth it in the long run. The temp never once pegs above 204 at the TC in 4th gear. Its constantly shifting in 5th more than i would have assumed.

 

I installed a cooler in my 2021 400 miles after purchase. I intially saw trans temps of 220F unloaded going over bridge in Houston lol. Installed cooler, 74 mph pulling 5500lb boat to FLA from Houston, trans temp never got above 203F. That is in 5th gear and many times D. Only reason I didnt keep in D all the time was sluggish throttle response. WIth no load trans temps never gets above 195F. I was averaging about 11.5 mpg. Surprisingly even in very heavy rain events the trans temps didnt drop but a degree. Truth be told I dont even know I can read my trans temps anymore as I havent checked in over a year and forgot how to do it after cooler install.

 

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