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While I was able to find information on testing the ATF temperature sensor in the GF4A-EL manual I've got:

enter image description here

I was unable to find any info on the normal operating temperature of the transmission.

I'm guessing that normal operating temperature would be pretty similar across all ATX's, like it is for engines. IIRC, the highest I saw on mine was about 60*C.

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  • I don't know what the operating temp is, but would bet it's higher than 60°C (140°F) ... One of the reasons I say that is transmission coolers can be located in the cars radiator. The engine runs much higher than 60°C (usually ~90-100°C), which means the radiator would be running much higher as well. If the tranny was running at 60°C, it would be picking up heat instead of losing heat at that point, which would defeat the purpose. Jan 4 '16 at 13:54
  • @Paulster2 I just went for a 20 minute ride and it took almost that entire time for it to get up to 60*C, and as soon as I parked it started falling into the 50's, even though the coolant temp was around 101*C. There is an auxiliary tranny cooler on this model and the ambient temp was about 12*C. Jan 4 '16 at 14:22
  • It depends on where the temperature is being measured. If the sensor is in the fluid return path, with an external cooler I can see the fluid being that temperature.
    – vini_i
    Jan 4 '16 at 14:33
  • @vini_i It's located in the solenoids area. Jan 4 '16 at 17:39
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According to this paper:

Normal operating temperature for an automatic transmission is about the same as the engine temperature, i.e., about 195°F. The temperature inside the torque converter, while pulling a big load from a standing start, could easily rise above 350°F.

EDITORY NOTE: I'm seeing this same basic range at many different sites.

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  • 1
    I noticed while checking my ATF level that the two marks on my tranny dipstick are labled 25*C and 65*C. So I'm wondering if that upper mark label indicates the normal operating temperature? 65*C is 149*F. I've noticed that during operation the ECU reports the temp usually being around 79*C / 174*F during city driving on a hot day. That's a bit lower than your number, but it may be because this model is sold locally with an auxiliary cooler installed from the factory ( middle east temps and all ), however I live in the mountains where it's cooler than normal for the country. Aug 25 '16 at 17:48
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The critical thing is to keep ATF temperatures less than the oxidation temperature for the given ATF. For high performance or towing vehicles, a large external radiator helps maintain a moderate temperature.

All transmissions work best with warm ATF, and some are more sensitive to cold than others. For this reason most vehicles pump the ATF through a tube in the bottom of the engine cooling radiator. It serves two purposes, one to warm up the ATF, the other to cool it. While 130F radiator fluid may hardly seem "cool" to a human, it is cooler than hot ATF in severe service conditions.

A chart (with little to no sourcing information) that gives you some idea how hot ATF runs is here: http://v8sho.com/SHO/ATFTempChart.htm

This link gives some idea how ATF's are tested: http://www.intertek.com/automotive/atf/oxidation/

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  • Interesting info, but doesn't really answer the question. Jan 4 '16 at 17:43
  • Unless he gives his vehicle and transmission information, we won't be able to answer his question.
    – kmarsh
    Jan 4 '16 at 17:48
  • As you'll notice in the first sentence, it's a Mazda GF4A-EL transmission. While I don't think it really matters, it's on a 98 626 GF 2L. Jan 4 '16 at 17:54
  • @kmarsh - Robert is correct here and he is the OP. I'm not sure how this answers the question of Normal Operating Temp for an Automatic Transmission ... he's asking for any automatic transmission. Jan 4 '16 at 17:59
  • Unless Mazda published it, there may not be a single correct answer. It may just be an allowable operating range. Usually more specific information can only be found for vehicles sold for towing purposes (such as pickup trucks or large SUV's).
    – kmarsh
    Jan 4 '16 at 18:14
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If your ATF fluid gets above 275F, you are at risk of serious damage and should change the fluid ASAP and should pull over and let the transmission cool down. At 300F, you are looking at metal parts warping, seals becoming hardened/damaged, etc.

175F to 200F is considered ideal operating temperature for a transmission (some sources say 160-180), and 150F is considered minimum ideal operating temp.

If you only ever get the temp to 175F, your fluid could last 100k miles in theory; if you run at 195, you're looking at a 50k service interval. If towing, or driving hard, or driving up steep climbs with your torque converted unlocked, or sitting in hot weather in traffic often (things leading to higher temps), you should be changing your fluid more often.

Be aware that in winter, it's possible for it to take several minutes of driving for operating temps to rise to the 150F mark. It's considered ideal to let the vehicle idle until RPM's drop before driving (though newer cars don't always idle high when cold--no advice there other than get a trans temp or scangauge, or just idle for a few minutes when cold).

I've included some further reading. The first I summarized above. The second are the slides of a talk about ATF that includes a lot of valuable information and math and theory about how ATF functions within a transmission, which necessarily includes lots of information about temps. The third is the collected information experienced by a guy who closely monitored his transmission temps under a variety real world conditions carefully, plotted the data, studied it, and gave some conclusions he came to.

http://www.digi-panel.com/trannyoil.htm https://www.bobistheoilguy.com/automatic-transmissions-study/ https://www.thenewx.org/threads/thoughts-and-observations-on-engine-and-auto-trans-cooling.65980/

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