Trans temp towing question

I feel I've done a lot of research on this and am thinking I might be over thinking it.

Truck 2019 TRD DB LB with campershell. Using scan gauge for my readings


when pulling a +- 1000 pound utility trailer I keep the truck in 4s and trans temp and torque converter temp stay around 185. I have read a lot and was very concerned about trans temp when towing when I first started pulling a trailer.

Last weekend went camping. Truck not loaded at all. while driving through just the hills of Missouri trans temp got to 190, and torque convert temp peaked at 217, but then dropped once over the hill. Truck was in D.

my question is if the truck in D hits 217, meaning it should have been engineered for that. is it ok for those temps as long as I stay under 220 and not for a long time?

I'm amount to drive from St. louis to Denver and would really like to drive a little faster than 60/65 on the long flat highways of Kansas. I'm thinking of driving 65/70, temp permitting.

I will be pulling an empty 620lb raft trailer.

does trying to drive in 5s sound bad.

I've read some people say if engine isn't reving high enough then I'll have coolant issues and voltage issues. But my truck regularly up shits to to early and bogs down the engine at 1.5k, so i'm thinking i should be fine.

 

In the Colorado Mountains in the dead of winter I have seen trans temps peak around 224 on my rig in S3 w/ ~3000 lbs behind me going through headwinds gusting to 50+ mph. I'm in a 2021 DCSB TRD Sport Auto so my rig comes with the thermostat set to 190 and the ambient temps were in the low single digits as I went from Denver through the mountains to Salida and both TF1 and TF 2 sat at 190 - 195 the whole way. I'm not sure if the '19 TRDs have the same thermostat settings but it sounds like you are doing everything right. As long as you are not sustaining those temperatures for very long you should be good.

I believe the towing bible linked in my build thread towing post has some information about temperatures and how they effect the life of ATF. I don't like temps in the 190s, I like temps in the 170s so I am going to add an external cooler and fan pack in the next month or two. I plan on pinning the trans open and running a Setrab 900 series cooler in series with the factory hardware for towing and long, slow climbs while wheeling in the desert where trans temps can soar to 240+

Driving in S5 is not bad, I do it all the time and have no issues. I spend most of my time in S4 though and had to keep it in S4 across I-80 going 70-75 Mph in a strong headwind because the trans was hunting for gears. No issues whatsoever. Just watch your TF2 temp VERY CLOSELY when in S5 or S6. When you start to see the temps rapidly climb it is time to downshift into S4 and you'll see temps rapidly fall.

Edit: typo
Edit 2: added last paragraph
Edit 3: added a pic so you can see what I tow - others tow much heavier than I do successfully

 

There are a lot of posts about tranny temps when towing.

Some of my observations:
My 2021 SR5 generally runs at 188-192 not towing and 192-195 towing 3500# trailer. In 100* heat may be 2-5*s warmer.
My 2015 ran about 10* cooler.

I added a cooler on both. On 2015 running temp dropped by 5-10*. On my 2021 the running temp was not reduced, but it did help in keeping the pan temps from climbing fast when going uphill, and thus kept the TC temps a bit closer to 220'ish when climbing. My tranny cooler doesn't kick in until temps are 185, and I understand that the tranny has a thermostat to bring it up to temp sooner.

In talking with tech engineers at Mobil, temp spikes in temp do not impact the life of the tranny fluid and do not have a material cumulative impact on the life of the tranny fluid. However, if your temps are over X* for 30+ minutes on a frequent basis then expect a shortened life.

The above being said, I plan on changing my fluid out approx every 50k miles (or maybe just spill and fill and ck level every 20k-30k), mostly due to the higher operating temp.

 

Reviving an old thread; I recently installed an ultraguage as I wanted a scan tool, and being able to actively monitor things through the ultraguage sounded like a fun selling point. That being said, I've been watching my trans temps for a couple months now and I'm not entirely sure what is "acceptable" or "preferred." I don't have any over the top mods on my truck, just lift/tires/camper shell/a little added weight, but my temps seem to be steady between 185-200 on any normal commute, NOT towing anything. Towing a small utility trailer, using ECT and S4, I saw closer to 200 average and spiked up to around 218ish a couple times. I'm not very well versed on trans temps, but this seems high to me. If these temps are in fact high, under normal driving conditions, in relatively flat terrain/mild weather temps, what would that be an indicator of? Could low trans fluid level bring on high temps? Truck has tow package with cooler I believe for reference.

 

Are the temps your pan or torque converter temps?

either way they seem ok. Short-term temp spikes have no impact on shortening the ATF life, per techs…
I found my towing temps are only slightly higher than not towing, mostly due to good temp control engineering.

 

both pan and converter; they're typically within a few degrees of each other at any given time (as far as I've noticed when at operating temps). I've noticed on my daily commute, I'm usually around the 190 range at any given time. My main question is (if lower temps should be expected) can higher than average temps be an indication of low trans fluid? I've read multiple threads about being underfilled from factory, and I've admittedly never checked the level or done a change, although I'm getting ready to do a series of 2 or 3 drain and fills. I suppose I'll answer my own question if temps improve after that.

 

All of these temps seem in line with mine. 193 avg coolant temp. Max of 205-ish.

TF2 seems a little more subject to change. 180-ish not towing. Max of 219 towing ~4,000 lbs uphill.

TF1 seems more stable at 190-ish, consistently, while not towing. Never looked at it while towing, since I always figured it would be =< TF2.

 

IMO the temps seen are ok. "Prudence" is the keyword: Don't beat the snot out of it going uphill on a long grade with it floored trying to keep up your speed: it will never forgive you. If you can't help yourself, at least try to keep it in "4". (or out of OD) If you have a direct reading method for the temp, then trust your gut and back off a bit when you see the temps that are trying to warn you off. If you've had an event where the temps approached or exceeded the comfort zone for the transmission: change the fluid at 30K instead of 60K and/or at the end of the season: it takes a lot of transmission fluid changes to equal or exceed the price of a new or even a re-built transmission: I'm guessing $5,000 p&l minimum for either.

If I was towing something larger or heavier than a big tent trailer 2-4,000 lbs) in the Rockies or the Appalachians on a regular basis: that's what I would do. YMMV

 

Good info, thanks everyone!