2019 tundra transmission thermostat location

One member contacted Valvoline re the temperature where MaxLife full synthetic fluid degradation begins. Valvoline told him degradation starts for full synthetic MaxLife at about 280 degrees, and as the temperature increases, the rate of degradation accelerates. I don't think even a full synthetic fluid will substitute for not having the cooler.

I'm guessing the alarm light was only on a short time? Your fluid sample actually sounds in good shape, but I would bet the level is now slightly low. If you change it yourself, you'll want to search here for the level checking procedure. Make sure you are looking at the procedure for the 5.7L. There is also a procedure for the 4.6L, and the temp checking ranges are slightly different. You put the truck in fluid level checking mode, and the instrument cluster tells you when the temperature is right for fluid level checking, and when it's too hot for checking.

 

Yes, the warning was on for about 10 seconds before I put it in N, then Park and it immediately went away. I shut the truck down for about 30 mins after that.

May I ask why the fluid is likely low now? Is it the amount that I sampled or is there some overflow tube or something like that which dumps fluid?

 

Were you monitoring your trans temp ? If yes , how much did it reach ?

I have crewmax 2019 , I went last weekend camping towing my 4000 lb trailer , i always tow on s4 driving 60mph and never exceed 217 on pan and occasionally 230 on torque when slowing down and accelerating . Last weekend saw around 214 on pan (that was highway in MA flat ground with some hills ) to note that I have been to Vermont on hilly roads with almost same kind of results

 

I explained above.

Having the fluid level at the correct level is a "moving target" which changes as the temperature changes. The level is only correct when overflowing at the check plug between 99-111 degrees. If you remove the check plug at 120 degrees, then some of your "correct fluid level" is going to run out on the ground because the transmission fluid expanded more as it got hotter. It likely won't be much...I expect you replaced the plug as soon as it started pouring out.

 

No I wasn't monitoring my transmission temp, there's no gauge on my dash for transmission.

 

Ah ok, yes that makes sense.

 

You need to use an odb2 reader and download a compatible app on your phone with the right pids to be able to see it. Lot of information on this in other threads , I am using veepeak odb2 reader and ODB fusion app on my iPhone with the Toyota codes to keep an eye on temps while towing

 

Lots of great info today! Thanks to everyone!!

 

Were you on D (drive) while towing ? Also did you have tow / haul activated ?

 

Yes to both.

 

Most probably why your transmission overheated as it kept haunting for the right gear.
From my experience towing my 4000lb , the transmission will go over 220 when I use s5 .
Never tow on D, use S4 with tow /haul and down shift if needed on hills . Try to keep your speed between 60 and 65 on flats and 55 to 60 on hills , that will keep things a bit under control.
For me it is a must to have the odb2 reader to monitor my temp , in this way I know when to stop if needed to let it cool down before things go south.

 

Thx Joe, this is good info.
I never had the issue with my Gen 2 equipped with a cooler, but this 2020 is a different beast.
I'm learning as we move along

I do love truck though.

 

Yes , I love mine too , I will be asking dealer to perform transmission oil flush as well as the diff on 30k , I tow like 6 to 7 times a year my travel trailer , so 214 to 217 f are ok for me , I would definitely get the external cooler if towing constantly heavy loads .
Enjoy your truck

 

My pan temp rose to 229F in 4S running around 60mph on terrain that wasn't challenging. My feeling is that if your keeping the truck for any length of time and you tow even occasionally a cooler should be considered. The current body style Tundra has been out since 2007 with the same powertrain. I find it hard to believe that it took them 12 years to discover that an external cooler isn't needed. Toyota went to the new 1234yf freon in 2019 and had to change the design of the condenser. Because 1234yf isn't as effeicent in cooling as R134A it wasn't possible to use the AC to cool the tranny like in pervious years. Cheapest solution was to eliminate the cooler for the remaining two model years and call the warmer a cooler/warmer.

 

Was that towing ?

 

Yes

 

So true RB, I'm having a tough time finding a cooler kit but will keep on it.

I keep my tundras about 10 years on average. Towing heavy loads is only 1-2 a year (6000lbs) but regardless a cooler is extra insurance.

 

Where are you on your cooler retrofit? Last I saw, you had all the Toyota parts lined-up and ready to rock...I guess you're waiting on the heat exchanger?

 

Just saw this thread and will mention that after adding a cooler to my 19 I just towed 350 miles or so to Creston BC today and never hit 200 on the pan temp. Towed pretty much the whole way in 5th except for any decent climbs when I shifted to 4th. The pan would hit 195 and level off there in climbs and once over it would be back to 185-188 give or take.

 

WOW, what cooler kit did you install?
I'm also in CGY Alberta.

 

I pm'd you.

 

Were those temps with the thermostat pinned or unpinned ?

 

Unpinned. The highest I noticed the torque pan was around mid 220's on steeper grades.

 

Ok yes . Yes that's about the same as my temps are now with my cooler setup . They seem to match engine coolant temp now

The 220s is accurate for the torque converter temps . Shouldnt worry because the fluid travels from the converter straight out to the cooler before it returns to the trans. So there won't be any heat soaking to the pan temps anymore

I haven't tried mine pinned when towing . I'm interested to see where the temps will like to sit once its allowed to fully flow continuously .

 

I just got it all installed on the weekend. I haven't pulled anything yet but unloaded temps are only 185f compared to around 200f before the cooler.

 

Congratulations. The retrofit will be worth the trouble.

Anyone have any observations/conclusions on the opening temp and operation of the thermostat? I've been curious about how Toyota's "melting wax" thermostat operates: Does the thermostat operate only "full open/full closed" resulting in temp fluctuation when cool fluid comes back to the transmission? Or, does the thermostat reach a "partially open" equilibrium point maintaining stable fluid temps according to load?

 

Good information on how the thermostat works from Infostream.

 

I also have that file from another source.

Reading again, I saw a slight clue that the thermostat might actually work by expansion of the wax and not necessarily by "change of state" or melting of the wax: "When the ATF temperature changes from low to high, the wax will expand to start to open the poppet valve and close the bypass valve...". If the thermostat works by "expansion" of the wax, then the action of the thermostat may adjust linearly according to the fluid temperature, i.e. partially open sending only some of the fluid to the cooler. If the wax has to melt for the thermostat to operate, then it would probably be either "full open" or "full close".

There's not enough tech data there to be conclusive, but guys with the coolers and OBD temp monitoring can probably tell what's going on from the behavior of the temperatures.

 

I believe that's how it works. It controls the amount of flow based on temperature similar to how a coolant thermostat works.

 

I pull a 9500 lb travel trailer and my trans temp is definitely not cooler than My ‘17 was. I’m adding a trans cooler to it.