how hot is too hot for auto transmission fluid?

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    how hot is too hot for auto transmission fluid?

    My GF has a 2004 Toyota Matrix with auto tranny and 220k miles. Tranny fluid looks and smells ok. It runs and shifts fine.

    Our drive home from town consists of about 20 miles of a canyon highway mostly uphill and then about 6 miles of fairly steep dirt road. The Torque app shows the tranny fluid gets to about 250 degrees by the time we make it all the way up the mountain. If we are driving around town the fluid stays at about 150 degrees or so. The tranny cooler is in the radiator and the electric fan works fine. The coolant temp gets to about 210 or so.

    Is 250 degree Fahrenheit too hot for ATF?

    #2
    https://www.tciauto.com/trans-life-expectancy

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      #3
      The ideal operating temperature of transmission fluid is 175 degrees. Overheating occurs after the temperature surpasses 200 degrees, and the failure rate doubles for every additional 20 degree increase after that.

      from google

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        #4
        Looks like I need to get an external cooler for that thing. thanks guys!

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          #5
          No, you need a manual trans for it.
          Safety Third!

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            #6
            Originally posted by jeeptj19992001 View Post
            Good info there. Quick Hijack: Is there such a thing as running too cool? My operating temp on my burb is 150 degrees and only reaches 180 when towing through the mountains....

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              #7
              Originally posted by backchat View Post

              Good info there. Quick Hijack: Is there such a thing as running too cool? My operating temp on my burb is 150 degrees and only reaches 180 when towing through the mountains....
              nope

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                #8
                https://streetsmarttransmission.com/...ication-guide/

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                  #9
                  250 is fucking super hot and the fluid is probably roached. Maybe not, but a home done flush is alot cheaper than a rebuild months/year(s) from now.

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                    #10
                    I generally shoot for 180ish

                    warm enough to evaporate moisture and reach full viscosity.
                    not hot enough to kill it.

                    250 is kills it temps.
                    Penguins can't fly, I can't fly, therefore I am a penguin.

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                      #11
                      my old motor home saw 275 towing from durango to silverton. and it was 40 degrees out. i sold it 5000 miles later. i was impressed with that turbo 400.

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                        #12
                        Fun fact, ford's 6r80 trans has a thermostat built in that doesnt open til trans hits 190. My '13 f150 ecoboost generally sees 205 to 215 towing my jeep/camper in hills from tx to pa to ut. Just changed/flushed the fluid for the 3rd time at 189k miles.

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                          #13
                          Originally posted by j20brett View Post
                          Fun fact, ford's 6r80 trans has a thermostat built in that doesnt open til trans hits 190. My '13 f150 ecoboost generally sees 205 to 215 towing my jeep/camper in hills from tx to pa to ut. Just changed/flushed the fluid for the 3rd time at 189k miles.

                          Yeah, I'm not sure the temps posted above are accurate for modern fluids/transmissions. My 2016 350 trans runs at 200 unloaded and will get up to 215+ towing. Fluid is not burnt but due for a change.

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                            #14
                            I always like to see below 230 degrees on atf temps. I've noticed a big drop in temps ~15-30 degrees when i replace shitty atf with tractor hydraulic oil. ATF really loses its ability to lubricate at higher temps i think mainly due to its low viscosity.

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                              #15
                              Originally posted by Arps View Post
                              The ideal operating temperature of transmission fluid is 175 degrees. Overheating occurs after the temperature surpasses 200 degrees, and the failure rate doubles for every additional 20 degree increase after that.

                              from google
                              Definitely not accurate. 6R140 trans in Superduty's runs 200F all day but don't go much over 215F towing heavy.

                              I am thinking your converter is unlocking causing the heating, watch that PID in Torque to see if it is being told to unlock or if its slipping.

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