Auto Transmission Temperature - Ideal?

What is the ideal temperature for a transmission to run at? And specifically, are there any issues with it running at only 125* in the winter?

Since I added a larger cooler, in cool/cold weather, especially when not towing a trailer, the transmission does not heat up.

I am wondering if I need to add a bypass valve to cut the cooler out of the circuit on cold days.

 

I have a factory cooler and it seems to run between 110-150 in the winter. I RARELY see it match the water temp on the scan gauge when towing. These trucks seem to take very good care of themselves. FYI I have a 2nd gen 2015 4.0 TRD Sport DC with towing package. I just changed fluid yesterday and had trouble getting the fluid temp to 115-130 to check the level. I settled for 108 after 40 minutes of trying to get it warmer. Mr. @gearcruncher seems to have gotten stuck with the transmission questions. He has MANY posts on our truck's transmissions, issues, and troubleshooting. Start reading here: https://www.tacomaworld.com/threads...th-pics-for-second-gen-4-liter-trucks.289913/
Scroll down and you will find the temperature/fluid life expectancy table. Anything 175 and below is golden... Temporary spikes up to 200 is ok but not if sustained. I tow with my 2015 a lot. Usually around 3-5000 lbs. I flushed it myself at 55k. The fluid was not burnt and still mostly red. It was time for it to go IMO. I also added LubeGard Platinum as it comes highly recommended by the gearcruncher. I think the most important thing for longevity is monitoring your temps, and clean fresh fluid every 50k. If you do decide to swap the fluid then it seems that the Toyota OEM WS fluid is not all it's cracked up to be. Keep reading threads and ignore the negativity. We are very lucky to have a transmission guy that will respond and help.

 

mine seem to run at 55 celcius, which works out to around 140 or so. If I'm doing a long freeway trip that is mostly flat, the TC doesn't unlock for a long time and it will run really cool, 45 celcius which is approx 120 ... The tranny seems to be happy and shift well anywhere between 0 and 100 celcius

 

Just running around town my truck trans runs around ~140-160F (pan and converter temp). On the beach and trails 200-210F (again pan temp), is not unusual; I have seen converter temp spikes of 285F.

 

https://www.tacomaworld.com/threads/transmission-coolers.526283/

 

I appreciate the responses. However, neither answer my question.

I am asking about a minimum operational temperature. In other words, my cooler cools exceedingly well - almost too well on cold days.

For the record, I have read and posted in both of those threads (other info, not my current question), I change my trans fluid every 15 - 20K miles, run a larger aftermarket cooler and an external filter. And use Valvoline Max Life DEX-MERC, which is WS compatible.

 

Yes , you can overcool . At temps such as 50 below zero , your transmission fluid is almost in a gel state and requires the assistance of the engine internal radiator to warm the transmission fluid on initial start up . With this said , what aftercooler did you purchase ? Quality aftercoolers come with built in thermostats that automatically bypass at these low low temps . You are not going to hurt your transmission running at 120 -160 .

EDIT under perfect conditions , your transmission should ideally operate at the FSM spec of 176 degrees . Thats where the designers of the fluid prefer it to run .
You do have the option of plumbing your aftermarket cooler before the rad cooler . this will reduce the heat load on your rad and allow the engine to warm the trans fluid to 176. I hope the OP appreciates the response as this does in fact answer his question

 

Bumping up . The OP wanted the specific temp number as shown in the edit in the above link