RV Tech Tips article on transmission temperature

[ShrimpBurrito]

That's great, Scott! I'm glad it works for you. Apparently 05 and 06 Sequoias and Tundras are the main cause of the headaches. I contacted Aeroforce at Bill's suggestion about their Interceptor, and they too have problems with at least these vehicles -- just in reading tranny temps.

Bill - thanks for that link. Very informative. I've already got an inline filter I want to install when I get the ATF changed.....I may look into an inline sensor as well. As you say, the actual temp is not perhaps as important as temperature swings/trends.

Dave

And speaking of temperature...what would be ballpark figures for desired operating temps for both the trans and engine coolant? Or does it vary significantly by model. I agree that the number reported on the gauge may or may not be correct and that a change from the usual could be significant. Just sorta curious...

[Bill]

Originally Posted by Scott O

And speaking of temperature...what would be ballpark figures for desired operating temps for both the trans and engine coolant? Or does it vary significantly by model. I agree that the number reported on the gauge may or may not be correct and that a change from the usual could be significant. Just sorta curious...

Scott -

I can answer only for my Explorers. On both of them, in normal driving, the trans temp always came up to about 180 degrees, and held there. It is so steady that I suspect it is thermostatically controlled somehow, though I don't know if that is true. Only under heavy load (towing uphill or against a headwind) does the temp start to climb above that.

I have not monitored engine coolant temp, but I think it is supposed to run about 220. It doesn't boil because it is under pressure. We have better automtive engineers than I on this board, so I may need to be corrected on this.

The reason for such a high temp has to do with the thermodynamics of an engine - a hotter engine is more efficient in terms of MPG. And everyone, especially the government, is obsessed with MPG today, right?

Bill

[ShrimpBurrito]

Originally Posted by Scott O

And speaking of temperature...what would be ballpark figures for desired operating temps for both the trans and engine coolant? Or does it vary significantly by model. I agree that the number reported on the gauge may or may not be correct and that a change from the usual could be significant. Just sorta curious...

ATF temp plays a role in when the ATF itself starts to degrade, as well as seals hardening, varnish formation, etc., and I doubt those points vary much by model. The charts at the beginning of this thread illustrate some of that, so absent any model-specific or anecdotal info you might find, they might be good to rely on.

Originally Posted by Bill

I have not monitored engine coolant temp, but I think it is supposed to run about 220. It doesn't boil because it is under pressure.

Not only because it's under pressure, but because the boiling point is raised by the antifreeze. My experience is the same as Bill's - usually around 220, although if you are towing uphill in 120 degree heat with the AC on, it's definitely going to be significantly higher.

Dave