ECT and S4 when towing using 2019 Tacoma

S4 keeps the tranny from shifting above 4th gear. The ECT button has the transmission use and Engine Controlled Transmission, aka more aggressive shifting. The manual suggests using S5 or lower and ECT. I have found that when towing my 3000# trailer (generally between 62-65 per GPS 64-67 speedo) that using S5 there is still a lot of shifting into 4th, even on flat roads. Also have observed that mileage is same, or sometimes minimally better, using S4--I suspect due to it not shifting as much.

For me tranny temps are slightly lower with S4, again due to less shifting, regardless of whether or not ECT is used... I do/used to use ECT.

I got Overland Tune a while back... love it, both towing and not towing.

 

I live in Southwest Florida (It's HOT) I have a 2022 3rd gen Taco with transmission pinned, pulling a loaded aluminum 5'X10 trailer with motorcycle (approx 1900# loaded). I have Scan Gauge readings regularly at 195 to 205 degrees pulling down interstate at 75 mph, running in 5th gear. I was wondering if any of you have any comments about running this hot. I am getting ready to leave on a 2000 mile round trip so I will be doing 8 hour day driving. Thank you in advance for any input!

 

You’ll be fine.

 

That's not hot at all IMO.

 

When i was in S4, it shifted to S5 and stayed there on the flats going 65 mph. When the truck came to an uphill grade on the highway it downshifted back to S4. I could leave it in S5, but the transmission tended to hunt when coming to any small uphill grade instead of remaining in S4 if left there. Imo, the transmission does hold the S modes longer till it reaches a certain rpm.

 

My 2021 runs hotter than my 2015 did. Generally, my 2021 pan temp runs at 190-195 when towing at 65'ish, my 2015 ran closer to 180 when towing. When not towing my 2021 is only a tad bit cooler. I do run a moderately large cooler. The cooler did not materially reduce my running pan temps for the 2021, though it did for the 2015. And I can confirm it is working by feeling the input and output hoses. Where the cooler does seem to help a lot is when I am climbing (or decending) and the TC is pumping out 215-225 temps and the pan temps are much slower to rise than before I put it on.

As such, your temps seem to be in-line with what I would expect on a 3rd gen. It is also why I am replacing my fluid on a quicker basis.

 

My best advice is to use S4 and S5 based on the road upcoming and observation of the shifting behavior. You will develop a feel for switching modes to minimize hunting and keep the converter locked.

The other observation, if it's flat let cruise do it's thing. Use your foot on hills, the trans seems to hunt way more with cruise on.

 

Trip report----ATF readings in Fl. and Ga. traveling at 75 MPH (no cruise control) using 5th on flats and downhills and 4th on up hills were between 195 and 210. In the mountains of Ga. and NC traveling at 70 to 75 MPH the highest it got was 220 (very briefly) but stayed between 200 & 215 depending on Tranny shifting. Gears in the mountains between 3rd (up steep grades) and 5th (downhill-flat). Gas Mileage report---- 13 MPG average on trip--best 14 MPG, worst 11.26 MPG (mountains)

 

How much weight were you towing?

 

3rd gens have a transmission fluid thermostat, unless you pin it open it doesn't matter how big a cooler you use the temp won't go below 190ish.

 

This is very similar to what I see.

 

I only tow a small trailer with an atv when I tow. Turning on the ECT Power button and using the S mode on gearshift selector. I use S5 on level and downhill grades and manually downshift to S4 when hitting an uphill grade. Works well for me.

 

It's pinned

 

loaded aluminum 5'X10 trailer with motorcycle (approx 1900# loaded)