Transmission Temperatures and How it Relates to Life of the Fluid

[mtbtim]

BTW, if anyone thinks 120-150 degrees is too cool, try warming up some trans fluid in a pan on your stove to that temp, then pour it on your hand.

Come back and report your findings.

All due respect Big Fish, you can't really compare humans to automatic transmissions. Humans run best around 98.6 degrees fahrenheit. Of course we're going to think 120-150 degrees is freaking hot. From my reading on automatic transmissions fluid temps, a good range is around 150-180 degrees fahrenheit. If you're happy with your set-up that's all that counts. I'm pretty happy my set-up but I think it would be nice to add an electric fan for the situations where the temps are climbing near 200 when I'm in the mountains.

 

[BigFishAllDay]

All due respect Big Fish, you can't really compare humans to automatic transmissions. Humans run best around 98.6 degrees fahrenheit. Of course we're going to think 120-150 degrees is freaking hot. From my reading on automatic transmissions fluid temps, a good range is around 150-180 degrees fahrenheit. If you're happy with your set-up that's all that counts. I'm pretty happy my set-up but I think it would be nice to add an electric fan for the situations where the temps are climbing near 200 when I'm in the mountains.

I wasn't really going for an apples to apples comparison there, my point was that at those temps the fluid is by no means cool. At those temps, trans fluid also pours like water. The underlying theme in all the research I did was that the no.1 enemy of an auto is heat, so I simply eliminated the chance of my trans getting too hot.

Like you said, whatever works best for your own setup. I like having the extra cooling capacity and peace of mind without the need for complicated add-ons, switches, wiring, interaction from the driver, etc.

Everyone is right, in their own right.

EDIT... btw if you view the post in my build where I installed the second cooler, I had some different ideas at the time, and was planning to someday route the trans through the rad, then through the two coolers. I also made mention that the running temps might be "too cool". Since then I've had some time behind the wheel and found myself happy with the current setup, and as a result my viewpoint on the subject has changed. Experience is the best teacher and we all experience different combinations of situations with our 4Runners.

 

[mtbtim]

I wasn't really going for an apples to apples comparison there, my point was that at those temps the fluid is by no means cool. At those temps, trans fluid also pours like water. The underlying theme in all the research I did was that the no.1 enemy of an auto is heat, so I simply eliminated the chance of my trans getting too hot.

Like you said, whatever works best for your own setup. I like having the extra cooling capacity and peace of mind without the need for complicated add-ons, switches, wiring, interaction from the driver, etc.

Everyone is right, in their own right.

I hear what you're saying and agree that excessive temperature is the killer of most transmissions. But, by doing a stand-alone external set-up like yours, you are consistently running below the optimal temperature range of the fluid. I'm not a chemist or mechanical engineer, but if the temperature of your ATF is constantly on the low side, are you now reducing the lubricating properties of the fluid, and thus lowering the life expectancy of your transmission? I don't know. Maybe someone with a lot more knowledge on fluid operating temps could chime in. I'm curious, I know Albuquerque gets fairly cold in the winter time. What kind of temps is your trans showing on sub-freezing days?

 

[BigFishAllDay]

I hear what you're saying and agree that excessive temperature is the killer of most transmissions. But, by doing a stand-alone external set-up like yours, you are consistently running below the optimal temperature range of the fluid. I'm not a chemist or mechanical engineer, but if the temperature of your ATF is constantly on the low side, are you now reducing the lubricating properties of the fluid, and thus lowering the life expectancy of your transmission? I don't know. Maybe someone with a lot more knowledge on fluid operating temps could chime in. I'm curious, I know Albuquerque gets fairly cold in the winter time. What kind of temps is your trans showing on sub-freezing days?

Optimal according to whom?

If an automotive engineer with specific expertise in automatic transmission design/operation, and/or a chemical engineer with experience in lubricant design/formulation wants to get on the forum and cover the topic, I'm all ears. If they were of the opinion that those temps are damaging my trans, I'd be open to re-routing my lines.

Beyond that, these types of threads on all forums are 99% opinion and interpretation... based on personal experience and things we've read on the web.

I run 120-130 after the trans warms up during winter. It takes 7-10 mins to reach max operating temp on colder days, depending on how I drive.

 

[LittleCaesar]

I think BFAD's coolers both have a LPD in them so they won't fully open to either 170 or 180.

Having the 70264 myself run in-series with the radiator cooler in addition to a spin on filter in the front, I can say that the 70264 fully opens up at 180. The highest temps I have ever seen is 200 towing a 22ft boat loaded. If I lived in a mountainous area I'd consider a 6" puller fan in front of my cooler or get a cooler with one built in. Also make sure the fan clutch is up to snuff.

Clean ATF works best. Always.

A good rule of thumb:

 

[mtbtim]

Optimal according to whom?

If an automotive engineer with specific expertise in automatic transmission design/operation, and/or a chemical engineer with experience in lubricant design/formulation wants to get on the forum and cover the topic, I'm all ears. If they were of the opinion that those temps are damaging my trans, I'd be open to re-routing my lines.

Beyond that, these types of threads on all forums are 99% opinion and interpretation... based on personal experience and things we've read on the web.

I run 120-130 after the trans warms up during winter. It takes 7-10 mins to reach max operating temp on colder days, depending on how I drive.

The web page I supplied a link to at the beginning of the thread said 80 degrees celsius or 176 degree fahrenheit is the temperature most ATF was designed to operate at. Where these people got their info., i don't know but they specialize in repairing transmissions so they know a hell of a lot more than I do. The read in my FSM that normal operating temps are somewhere in the 150-180 range. Can't remember the exact numbers. I also remember reading similar findings other places but I can't remember now. You could do your own Google search and I'm sure you're going to find sites to support what I'm saying. Later on, when I have more time, I'll do a search and supply some links so other people happening upon this thread can read up too.

 

[BigFishAllDay]

The web page I supplied a link to at the beginning of the thread said 80 degrees celsius or 176 degree fahrenheit is the temperature most ATF was designed to operate at. Where these people got their info., i don't know but they specialize in repairing transmissions so they know a hell of a lot more than I do. The read in my FSM that normal operating temps are somewhere in the 150-180 range. Can't remember the exact numbers. I also remember reading similar findings other places but I can't remember now. You could do your own Google search and I'm sure you going to find sites to support what I'm saying. Later on, when I have more time, I'll do a search and supply some links so other people happening upon this thread can read up too.

I'm not discounting that information... but...

Does operating at a temp below that at which the ATF was designed to operate damage the trans? Or does it merely result in reduced efficiency/mileage?

The FSM says that normal operating temps are 150-180... okay, but does operating at temps below normal range damage the trans? Or merely reduce efficiency/mileage?

Do you see what I'm getting at? Nothing, whatsoever, says that running cool is detrimental to the trans itself. I've never read that. Perhaps I'm giving up some mileage in exchange for my cool temps, but beyond that I'm not convinced there are any downsides.

 

[mtbtim]

I'm not discounting that information... but...

Does operating at a temp below that at which the ATF was designed to operate damage the trans? Or does it merely result in reduced efficiency/mileage?

The FSM says that normal operating temps are 150-180... okay, but does operating at temps below normal range damage the trans? Or merely reduce efficiency/mileage?

Do you see what I'm getting at? Nothing, whatsoever, says that running cool is detrimental to the trans itself. I've never read that. Perhaps I'm giving up some mileage in exchange for my cool temps, but beyond that I'm not convinced there are any downsides.

Ok, here's some links I found:

On the below link, see what it says at 150 degrees:
Transmission Oil

Read below what "Wysetech" says in his response to a member's question. He's been a certified mechanic for 47 years so he probably knows what he's talking about.
Can You OVER Cool A Transmission? (1/1) - EricTheCarGuy - EricTheCarGuy- Stay Dirty!

The below link is fairly informative regarding external coolers and operating temps. It says too low of temps allows condensation to build in the trans and it will lack efficiency.
AGCO Automotive Repair Service - Baton Rouge, LA - Detailed Auto Topics - Do I Need An Auxiliary Automatic Transmission Cooler?

The below link discusses overcooling also:
https://oldihc.wordpress.com/2012/11/28/automatic-transmission-cooling-2/

I think that's enough reading.

 

[BigFishAllDay]

So, in a nutshell, your links say:

Running too cool can result in condensation buildup and reduced efficiency. Got it.

I'm cool with the minor drop in efficiency. I'm still getting 16-17 mpg on trips.

As far as condensation, I guess that's a valid concern. What's the boiling point of water, though? 212 degrees, right? So anything less than that and you're not really boiling off any condensation in the first place.

Would you then derive that an auto needs to operate at 212 or above for a certain amount of time on a regular basis to avoid condensation? I know that's the idea with motor oil and avoiding short trips. The same research that you are forming opinions around suggests an optimum operating temp below that at which you would eliminate condensation from the system.

I'm not concerned about condensation. My 4Runner sees 5K rough miles a year, and I drive it for hours on end at 150+ degrees operating temps. On top of that I live in an arid environment and drain/fill my fluids on schedule.

I fully acknowledge your points, but I'm still not sure you're seeing mine.

 

[diverscale]

The only thing I don't like about the first article posted in this thread is their suggested way of changing the fluid.

This ''drain the pan and refill'' is not a fluid replacement at all.

 

[amalik]

[MENTION=120071]mtbtim[/MENTION], I think BFAD was just chiming in to give some insight to his dual cooler setup in case anyone else was interested.

I don't think anything you say will change his mind on his setup.

As he said, different solutions work for different people.

 

[mtbtim]

[MENTION=120071]mtbtim[/MENTION], I think BFAD was just chiming in to give some insight to his dual cooler setup in case anyone else was interested.

I don't think anything you say will change his mind on his setup.

As he said, different solutions work for different people.

Believe me, I didn't think I was going to change BFAD's mind. I'm just posting for other peoples benefit who are interested in the conversation.

 

[mtbtim]

So, in a nutshell, your links say:

Running too cool can result in condensation buildup and reduced efficiency. Got it.

I'm cool with the minor drop in efficiency. I'm still getting 16-17 mpg on trips.

As far as condensation, I guess that's a valid concern. What's the boiling point of water, though? 212 degrees, right? So anything less than that and you're not really boiling off any condensation in the first place.

Would you then derive that an auto needs to operate at 212 or above for a certain amount of time on a regular basis to avoid condensation? I know that's the idea with motor oil and avoiding short trips. The same research that you are forming opinions around suggests an optimum operating temp below that at which you would eliminate condensation from the system.

I'm not concerned about condensation. My 4Runner sees 5K rough miles a year, and I drive it for hours on end at 150+ degrees operating temps. On top of that I live in an arid environment and drain/fill my fluids on schedule.

I fully acknowledge your points, but I'm still not sure you're seeing mine.

I completely understand what you're getting at. Will lower temps hurt the life of your transmission? I guess you have to ask why we have thermostats in an engine and they open at a certain temperature and then system generally holds that temperature. I'm assuming part of that reason is the oil is at the temperature that will lubricate the engine most effectively. But, maybe I'm wrong. It's my thoughts that running a lot of the time below 150 degrees is causing your trans fluid viscosity to be less than optimal and thus not lubricating the trans as effectively. You stated your normal range with your setup is 120-150 so that's what I'm basing my comments on.

I've done my research and made up my mind what the best course of action was for me in dealing with the high temps I saw driving in the mountains. And, obviously you're happy with your set up and that's all that counts.

I started this thread to hopefully educate people a little about the dangers of running too high of temps and also the concerns of running too low of temps just like [MENTION=78997]Drcoffee[/MENTION] attempted in his thread regarding whether or not to bypass your radiator cooler. This way, people are more informed before they go down the road of either bypassing their radiator cooler like you or running it in-series like me.

 

[BigFishAllDay]

Know too that I wasn't trying to change your mind either, but figured I'd provide some counterpoints/reasons why I chose my current setup.

I actually enjoyed this exchange with you, [MENTION=120071]mtbtim[/MENTION] . It was civil (despite us having different views), and generated some valuable discourse on the subject of running w/trans temps that are on the low end, which is rarely discussed. You encouraged me to think through the subject again, which is never a bad thing, just to make sure I've covered all my bases.

 

[mtbtim]

The only thing I don't like about the first article posted in this thread is their suggested way of changing the fluid.

This ''drain the pan and refill'' is not a fluid replacement at all.

Your absolutely correct it's not a fluid replacement but it is still highly effective to keep your trans fluid in good shape and a lot easier than doing the more involved complete flush. I drain and refill my trans every 10,000 miles and I'm replacing approximately 5 quarts each time. Supposedly, not 100% confirmed, the fluid capacity of our trans is around 12 quarts so I'm renewing 40% of my fluid with every change. Over 30,000 miles, I've drained and replaced 15 quarts. If someone was doing a complete flush every 10,000 miles, that would definitely be superior to what I'm doing. But, if they're waiting a full 30,000 miles to do that complete flush, I'd argue that's not any better than my technique of renewing the fluid.

I have 322,000 miles on a Subaru Outback and the drain and refill is all I've ever done for the transmission and it's still going strong.

 

[StreetCreeper]

On a lighter note, this just seemed like a good place to use this little gem....

​

 

[mtbtim]

On a lighter note, this just seemed like a good place to use this little gem....

​

I like your sense of humor Woody.

 

[diverscale]

I drain and refill my trans every 10,000 miles and I'm replacing approximately 5 quarts each time.

Well, doing that every 10 k miles would drive me crazy.

You are wasting much more energy doing that pan drain and refill every 10K miles than I do doing a proper 100% flush, using the transmission internal pump every 60 to 100K miles.

It is not even that much longer than dropping the pan, since you actually don't have to drop the pan and just turning the engine on and off to flush out the trans fluid from the radiator return hose.

 

[mtbtim]

Well, doing that every 10 k miles would drive me crazy.

You are wasting much more energy doing that pan drain and refill every 10K miles than I do doing a proper 100% flush, using the transmission internal pump every 60 to 100K miles.

It is not even that much longer than dropping the pan, since you actually don't have to drop the pan and just turning the engine on and off to flush out the trans fluid from the radiator return hose.

Possibly you're thinking I'm taking off my transmission pan every time? I'm just unscrewing the drain plug, waiting a little bit for the fluid to drain, replacing the drain plug with a new crush washer, and refilling the system with around 5 quarts. I don't think it gets any easier than that.

 

[amalik]

Possibly you're thinking I'm taking off my transmission pan every time? I'm just unscrewing the drain plug, waiting a little bit for the fluid to drain, replacing the drain plug with a new crush washer, and refilling the system with around 5 quarts. I don't think it gets any easier than that.

Do you just fill to the low cold mark and call it good or do you do the whole operating temp thing and gear shifts and getting below hot mark?