Towing and Trans Temps

Hello all, I've been reading a fair amount about towing with a Tacoma and the positives and negatives. Pulled the trigger on a 21' travel trailer weighing in around 4000lbs. Went to pick it up and had a 180 mile trip home. Truck is a 2015 4x4 TRD, 22,000 miles, with towing package to include transmission cooler. On the trip back, truck towed it fine with the exception of the trans temps. Using an Torque Pro App, with the truck holding about 2500RPM and 55-60mph, TTemp 1 was over 230 and TTemp 2 was pushing 250 most of the time. Downshift to 3rd brought the temps down a few degrees. No hills, just flat South Texas roads. I figured the temps would be higher while towing, but this seems pretty drastic. Just curious what others are seeing out there and any ideas. Other than the temps, truck pulled everything just fine. Thanks in advance.

 

I tow a travel trailer with a dry weight of 4,500lbs in the Sierra Nevada mountains and haven't seen over 245f, even when pulling up the grade in the summer months. Were you towing in D?

That'll heat a transmission up pretty quickly.

 

Driving in OD will heat up pretty quick!

 

As stated above, dont use D. Also, you will want to consider adding an aux transmission cooler in addition to the factory one.

 

Should have stated that I was driving in 4, not D. How much of a difference are you guys seeing with an aftermarket cooler. I need to get a good 30 degree temp drop to make it in a reasonable range, not sure if I can expect that from a larger cooler. On another note, and pardon my ignorance, but what is the major difference between the pan temp and the outlet temp, i.e. which is more of a concern?

 

I've always used pan temp.

I'm wondering if your Torque Pro needs to be calibrated. What are your transmission temps at startup and during normal driving?

 

What was the outside temp? It hard to fight a high ambient temperature. A larger cooler could get you a few degrees lower but like you said I doubt you can get that much lower.

 

This was exactly my thought.
Here are the equations from my 2010. I don't remember which is the pan and which isn't though.

Trans 1
((((A*256)+B)*(7/100)-400)/10)

Trans 2
((((C*256)+D)*(7/100)-400)/10)

 

Ambient sounds were in the low 90s so definitely warm and a bit of a headwind didn't help either. Those are the same PIDs I have installed. On startup I'm running around 140ish and normal driving with low 90s ambient is around 180ish. Not sure about calibration, was under the impression it wasn't more or less plug and play. Appreciate the feedback guys.

 

Startup seems high. You should be closer to the ambient air temp before the fluid warms up.

 

This is what I did.
https://www.tacomaworld.com/threads/trans-temp-sensor.456998/

 

Ok just went to check startup temps and stickyTaco you are correct, looks like about 102 on startup which matches the air temp right now. Does 180ish sound normal for everyday driving on warm days?

 

That's about where I'm at...175 to 185f when warmed up and not towing.

 

Im not sure how the ATF sending unit is setup on the 2nd gen but ive been pinning the thermostat open while towing with good results. Im also running a larger cooler and my loaded trailer weight is about 3500lbs. It's rare my temp surpasses 190 and that's climbing hills in the AZ heat.

 

From comparisons, seems like I'm well above where I should be. Toyota dealer was of no help and said if the tranny burns up we will replace it under warranty. Not the answer I was looking for. Would think I should be able to safely tow something well under the weight limit without issue. May need to call Toyota direct....or just get a new truck.

 

You might want to look at this chart if your tranny temps are that high. You are already down to fluid changes at 10 to 20K.

 

Not sure how accurate that chart is. Seems the internet is full of these that all report different temps.

 

@bcats4life, here's some comparisons for you. The first pic is after towing 5k lbs on flat ground at 60 mph for 25 minutes and the second is after going up a decent grade at 65mph. Temps peaked at 240f going over the pass but quickly dropped back down to 215f, where it remained for the rest of the trip home.

 

I assume the chart is using Dino oil not synthetics? Synthetic oil would be about 25 degrees higher!

 

The third gen thermostat doesn't open until 195F, so that chart doesn't apply to us. I assume that's also not for WS