Transmission Temps

I bot a YOMB module and the only app that would work and show transmission temps was Car Scanner. I have 2 different temps so I assume one is pan temp and the other torque converter exit temp? Anyway, I was pulling my boat in Drive just to see what the temps were. The highest reading(TC?) averaged probably between 190 and 200. On long hills I noticed it hit 231 very briefly twice. I would say it was between 200 and 215 maybe 15-20% of the time, 190-200 60%, 221-228 was maybe 5% and 165-180 the rest of the time. Assuming the high app reading was the torque converter exit temp, are those temps too high?

Thanks

 

Sounds like normal temps with normal fluctuations.

 

Fluid degradation begins above 170F and is non-linear. That said, short excursions beyond that are normal and no big deal. 230 is not good. Looks like you are are reading your TC temp which is good. Pan temp will trail it quite a bit over short durations , but they will equalize over long durations. I'd suggest down shift into "4" whenever you are pulling a steepish hill. That will lock the TC and drastically reduce the TC temp increase. Search the forum for a discussion on temps/fluids by "gearcruncher" it will tell you all you need to know.

Per gearcruncher;

Rate of oxidation to double for each temperature increase of 20 deg F above normal (175 deg F). As oxidation rate doubles, useful life of fluid is cut in half.

At 175 deg F life is 100,000 miles
At 195 deg F (20 deg above 175) life is 50k miles
At 215 life is 25k miles
At 235 life is 12k
At 255 life is 6,250
At 275 life is 3,000
At 295 life is 1500
At 315 life is 750

 

So if my temperature reached 131 for say 3 seconds does that mean I need to change my fluid around 12K or I would say I averaged 195, should I wait for 50K?

Thanks

 

The way to think of it is you can run at 230F for 12k miles or 50k miles at 195F. It's mileage/temperature cumulative which seems a little weird because there really should be a time component. The calculation must be correlating time and mileage just as mileage for simplicity. Moral of the story is to try stay in the 170F zone as possible and discount fluid life from there by what you observe over time.

 

Pan temp is what you want to keep an eye on for sustained high temps which will degrade fluid. Torque converter exit temp is very brief and fluctuates lots.

Also if you have the tow package, its easy to space the stock auxiliary cooler up ~2.5in to get it in the line of air flow instead of blocked behind the grill, this really helps on hotter days when loaded.

 

Your temps seem about right. I mow for a living and tow roughly 2900lbs in a 6x12 homesteader intrepid enclosed trailer. I always keep my truck locked in 4th. I tried to tow in overdrive for about 4 times and didnt like how the truck felt like it was straining. These trucks, i agree with what one of the above said, just put it in 4th gear. It will keep your transmission from shifting so much. My transmission with my load at the converter will float around 185F when on flat ground. Once I climb, it will rise. @nd4spdbh , ive heard of guys doing that before. I might do that to my truck. Its stupid that toyota put it behind the grill. That would help a lot.

 

If I remember correctly, the thermostat doesn't even open until 189 or 190 F, so Toyota must believe that your trans temps are absolutely normal and to be expected.

 

Take that with a huge sack of salt! There are plenty of transmission still shifting just fine with hundreds of thousands of miles and still on the original fluid. Not saying it’s advised, just reality. On the Tacoma it is still relatively easy to change the ATF. On my Chevy it is retarded. I’m not doing that and just saving my energy/cash for if/when it needs a new transmission.

 

2nd gen tacoma 5spd auto transmissions do not have a thermostat, which is odd considering the same transmission used in the 1st gen tundra do. But thats besides the point.

Regardless Only use the tc output temps as a reference (its easy to see when the torque converter is unlocked as exit temps will climb compared to pan),

The real temp to keep an eye on is the pan temp.

 

I remember you saying you can see 2 trans Temps, if my memory serves without looking at my scan tool, 1 is the pan and 2 is the converter. You'll know which one is which. Like what @nd4spdbh said, the converter temp always fluctuates. The pan will always stay at a steady temp.