Transmission oil friction modifiers and temperature

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Is there anything in the transmission fluid for example friction modifier, etc. which needs a certain temperature (e.g. 190F) to activate?

basically is there a harm in running the trans fluid cooler than what they were designed for?
For example a truck designed to run 180-200°F range from the factory ... and you add additional or bigger trans cooler (for towing) to bring the temps down 150-170°F.

I was discussing it with a knowledgeable co-worker who says they design it that way (run hotter) to squeeze a little mpg but it's not good for the trans fluid in general ... However another knowledgeable friend says it need high temp to active stuff in the fluid.

I figured bitog can resolve the mystery!
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Old school temperature-activated (GL5) EP additive formulation had been replaced among others, by pressure-activated additives since .... to what degree IDK but I suppose it's substantial in automotive applications.
Heck, for all you know the so-called temperature -activated EP additive may still be in use in 'generally cooler' industrial gear train systems today.

However,I'm ignorant of temperature-activated AW additive package (GL4 )as used in non-differential transmission gear trains.

IME, in hot tropical ambients I had seen industrial gear train systems that had been 'traditionally' operating at between 45*C(115*F) and 60*C (140*F), with automotive systems trends towards higher operating temperature regimes partly due to space constraint leading to limited coolant capacity.

Hence I personally don't buy the concept of temperature-activated additive properties applications for transmission components protection,be it industrial or automotive, granted FE has been a marketing and selling point in the CAFE part of (automotive) world.

Just my
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Edit:The most basic and fundamental function of a coolant oil is for cooling, components protection and oil longevity (oxidation).
 
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Some of the late-model vehicles may hold trans temp high even with cold outside temps. On a little bit older vehicles, though, I've checked ATF after a 1+ hour highway run (at ~30F ambient temps) and the ATF is only lukewarm.
 
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Originally Posted by OilUzer
Is there anything in the transmission fluid for example friction modifier, etc. which needs a certain temperature (e.g. 190F) to activate?

basically is there a harm in running the trans fluid cooler than what they were designed for?
For example a truck designed to run 180-200°F range from the factory ... and you add additional or bigger trans cooler (for towing) to bring the temps down 150-170°F.

I was discussing it with a knowledgeable co-worker who says they design it that way (run hotter) to squeeze a little mpg but it's not good for the trans fluid in general ... However another knowledgeable friend says it need high temp to active stuff in the fluid.

I figured bitog can resolve the mystery!
grin2.gif




Your question is really to general to answer properly without typing out a book for all the difference cases that are possible.

Generally transmission fluid will last longer cooler, but there is a recommended temp. range. more for the viscosity of the fluid and efficiency.
My Jeep is 150f-165f in normal driving, and abit higher on mountains or towing and the transmission fluid we have in modern vehicles is improved over 20-30 years ago.

Second poster who replied from Malaysia is talking about gear oil which isnt what you asked, and are usually splash lube not pumped so they most dont have "coolers"
 
Originally Posted by OilUzer
Is there anything in the transmission fluid for example friction modifier, etc. which needs a certain temperature (e.g. 190F) to activate?

basically is there a harm in running the trans fluid cooler than what they were designed for?
For example a truck designed to run 180-200°F range from the factory ... and you add additional or bigger trans cooler (for towing) to bring the temps down 150-170°F.

I was discussing it with a knowledgeable co-worker who says they design it that way (run hotter) to squeeze a little mpg but it's not good for the trans fluid in general ... However another knowledgeable friend says it need high temp to active stuff in the fluid.

I figured bitog can resolve the mystery!
grin2.gif



There is nothing in ATF that is temperature activated. All components work down to about -40F and up to 250F or more.

Continuous extreme high temps will degrade the fluid at a higher rate.
 
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