Trans Temps While Towing

Towing my 3700 lb trailer over Monarch pass has had me concerned of excessive temps, after a lot of research on here I decided not to put a cooler on and roll with it as is like Toyota and the dealers all say is fine. My listed trans temps are for the pan, not converter. Several trips in 95 deg temps never put me higher than coolant temp around 195. Large hills would see short rises up to 220 and quickly recover. I always tow in S4 and in the mountains it would quickly start rising if dropped to S3, a few times I had to grab 2nd gear and I was surprised that the temp would level off stay at 215-220. Converter temps would flare at 240 and once at 250 but only for a couple minutes. Overall it did great and I think the fluid should be fine if changed every 30k because the higher temps were for short periods of time.

 

For comparison I have a 24 with 30k miles. Live in south Florida bumper to bumper traffic. I’ve seen pan temps at 190-195 and converter once or twice above 200.

I’ve done a drain and fill already, color was dark, but did not smelly burnt at all. Shifting was the same more or less afterwards. Temps maybe dropped 5 degrees or so.

that’s without pulling any weight. Completely stock.

 

What year is your 4Runner, and how did you measure the temps? I tried purchasing an Ultra Guage only to find out that my 2023 does not offer up transmission temps at all. Looking for other solutions.

 

More than likely Scangauge 3. With the ultra gauge, is there a way for you to download more
Parameters like the Scangauge does?

new out of the box, once plugged in, Scangauge 3 comes with regular monitors, and X gauge monitors so you can see everything besides oil temp/pressure

 

Mine is a 2023, I use OBDLink MX+ bluetooth diag tool. You can easily create a dashboard on your phone with whatever values you wish. I use both trans temps, engine temp, and converter lock status. I purdy sure you can do it with your ultra gauge too.

The Mx+ is also a very capable diag tool that works for almost any vehicle so it does double duty.

 

Do you know which is the torque converter temp, and which is the pan temp? I’m only seeing these listed in OBD Link as Temp 1 and Temp 2.

 

I'll have to look next time but grab them both and it's easy to see, the pan temp is lower and more stable, the converter is higher and erratic.

 

we probably fooling ourselves to judge trans temp in an oil pan only. spike of trans temp at the "furnace" - trans converter - is the place where trans fluid gets burned and that requires us to change our driving or towing procedure to keep that temp down whenever possible. what trans cooler does good, if proper size and properly routed, makes the process of cooling trans fluid faster, than without it.

 

Torque converter fluid temp is reported in the data stream as well as pan temp. And you’re right, it jumps while accelerating uphill.

 

Temp 1 will be your pan, temp 2 will be your torque converter. After lockup, torque converter will more or less equalize with pan temp, until torque converter gets unlocked/flex lock in s4

 

I tow a 3300lb camper full time. I have toyota flush every 50k. When i go over monarch, i am not going over 3k rpm. That could be 25mph in s2 or 35mph in s3. Depends on section. Either way, i go over no passes fast.

 

I agree on the furnace analogy, but how long the fluid is in the furnace is a factor as well, the guy in this article below refers to it as flash and bulk temps. It takes some time at high temps to cook the fluid and luckily mine isn't at those temps very long as I don't hit mountains every month.

https://www.dieselarmy.com/ask-the-expert/transmission-temperature-how-hot-is-too-hot