Caught between cat thefts and a hard place

I don't notice a big difference in mpg between towing in D and S4. I'm seeing 8-9 mpg either way. I was just curious if he believed towing in S4 kept the transmission cooler.

 

He definitely communicated that towing in S4 uphill under load was a must for transmission temperature purposes. So basically The answer to your question is yes.

 

I resisted the notion of a cooler ferociously. I threw the towel in when my 2021 4runner would cruise around at 170-178F with an old school intank raditator cooler. And although f 250 and other oems are targeting higher and higher transmission temps, they also have additional systems to maintain the temps in the target range. There is none on the 19-21 Tundra.

With the full house MHX kit, I cruised with full payload in 108F temps, 78-79 mph, in rolling hills (the worst case scenario), and I never went above 190F on pan temp and TQ temp never got above 220F.

With a light or no load in bed I match the temps of my 2021 4 runner--cruises at 178-183F.

 

I tow an 8k fully loaded travel trailer from Vegas to Idaho once a year during the summer. Keep it in D with Th switch on. Never had a problem. The rest of the summer i tow the same TT around the west coast with no problems. I only have one tow with the SC installed up to Mt. Charelston. 13 miles straight of 7% grade. Worked real good. Love this truck. '18 sr5 double cab 4x4.

 

I towed a couple of times up that stretch to Fletcher; I think I got like 3-5mpg up that hill! Oh well!!!!!

It was still fun and at least 30° cooler (especially evening and night) than being down in the valley!!!

 

You have a factory installed cooler, so you are better off than the 2019+ models.