Heat and Transmission Failure Charts

[Silber Igel]

I've been looking at these charts over the last few days.....

Would anyone have information to share on the origin, background, development and history of those 'charts' we have all seen for forty years regarding transmission life and heat loads????

I've been seeing those charts.... no doubt the same ones I saw in the '60s.... now photoshopped to look glossier and snazzier ... and the information just doesn't seem to change.

Were these studies done on a '53 Buick Roadmaster with a Dynaflow transmission, or what???

Who did the tests?
When were these tests performed?
What were the test parameters?
What oil was used? Dino? Synthetic?
Do they mean anything in today's world of improved transmissions, coolers, and fluids?
Is the information relevant today or just more 'urban legend?'

It seems to me that the data in these 'time honored' charts is stale, without bona fides; and irrelevant in today's world.

 

[XS650]

Originally Posted By: Silber Igel
I've been looking at these charts over the last few days.....

Are you going to share them with us?

 

[Pablo]

What charts are you talking about?

 

[sciphi]

My $0.02 is that I added a cooler to my 1999 Buick LeSabre after Auto-RX cleaning and flushing the transmission, and it runs really nicely. It ran nicely before, and the cooler dropped 20* F off the fluid temperature. It shifts a wee bit better now.

I was told that by adding the cooler, I was extending my transmission's life. That's the urban legend spawned by these charts. You have me interested.

 

[c3po]

I believe that these transmission temperature charts are for the fluid life, meaning if the temp gets to 300 degrees the fluid is only good for maybe 1000 miles. My opinion is that transmission pan temperatures are misleading. I have an infrared gun and my trans pan is a Derale with cooling tubes in it. The pan temp because of the cooling tubes reads about 100 degrees, up on the pan a little bit away from the tubes it reads 150 degrees, my Torque Converter reads 160 degrees when I aim the infrared gun at it. My trans temps may be different from everyone else's because I have no A/C Condenser in the front, I have shorty headers and a dual exhaust with high flowing mufflers. I also Auto-Rxed the engine and transmission. This may also sound strange, I do not run any kind of mechanical fan or electric fan so I have unrestricted flow through my radiator. The only trans cooler I have is what is inside my radiator. I have been doing a lot of reading about transmissions and external trans coolers, the problem I see is that when the fluid in the trans pan starts to travel some goes to the cooler and some goes to the Torque Converter, I have not been able to tell exactly how much. Basically not all of the transmission fluid goes right to the cooler, it would be great if all of the fluid went to the cooler 1st and then to the torque converter and then back to the pan. I once had an external cooler plumbed into my cooler lines and did not notice much difference, but then again at the time I did not have an infrared gun. If you can get a higher capacity trans pan I am sure it would be beneficial. The charts you are talking about can be found on the TCI and Permacool website.

 

[Silber Igel]

Originally Posted By: XS650
Originally Posted By: Silber Igel
I've been looking at these charts over the last few days.....

Are you going to share them with us?

Sorry Boyz and Girlz!!!! Here's a linky to one :

http://www.txchange.com/heatchrt.htm

 

[c3po]

Thanks for the link, I believe the filter they are talking about might be a Magnefine which goes in the cooler lines. Filtermag makes a transmission pan magnet that goes on the bottom of the trans pan and traps particles down to about 2 microns whereas the Magnefine traps down to 25 microns, most transmission filters in the pan only trap down to 100 microns, before any one thinks I do not know what I am talking about I have 362,000 miles on my transmission and nothing has been touched on it except fluid and filter changes, and of course 6 ounces of Auto-Rx.

 

[Silber Igel]

Sorry,

I'll say again.....

What's the provenance of these 'heat vs. life expectancy' charts that are so widely publicized ... and have been since the '60s???

Who did these tests?
What ATF was used? Dino? Synthetic??
How was the test conducted?
Do you think the test is still valid today given improvements in technology, AFT fluids, metallurgy, cooling systems, etc..

Are they valid tests, still relevant today or are should they be relegated to 'urban legend?'

 

[XS650]

They still seem to fit recent anecdotal evidence of transmission life vs temperature.

Transmission have gotten more complicated and more highly stressed as they are downsized. Modern ATs if anything are harder on oil than the old ones.

A good synthetic would be more tolerant of overheating, but it's viscosity still drops and gives less protection to the machinery than oil at the design point viscosity.

I don't think you will get simple definitive answer to your question.

Ideal engine oil operating temperatures haven't changed in 50 years either. Synthetic oil is more tolerant of temperature insults, but it's still better to keep your oil temps within power train engineer's design goals. Only problem is, the power train engineer's aren't allowed tell you what their design goals were.

 

[c3po]

I do not know who did the tests or how it was conducted. They probably used dino atf, and yes the test whatever it maybe, is still valid today, I would not worry about the test but would instead try to identify your transmission temperatures and worry about that instead, if your temps are above 220 degrees then switch to synthetic transmission fluid and then check your temps again, if they are not at 200 degrees get an external trans cooler.

 

[BearZDefect]

I can estimate the ATF temperature in my RE4F04A (JATCO 4sp in 1997 i30) by:
- When the TCC starts to activate (my estimate about 100f)
- How it shifts from 1st to 2nd (serious guesstimate, loses the slight harshness around 150f)

Don't take that seriously, I haven't actually measured the temperature. Those are just two indicators of reaching two thresholds.

A recent exchange from Dexron III to Dexron VI doesn't seem to have changed the shifting. I just hope it helps reduce drag in the winter.

 

[Whitewolf]

I don't know the answers to your questions but I suspect that the charts are based on quite old mineral formulations.
If that is true then they will not take into account the advances that have been made in more recent years. For example let me use the changes in the running severity of the DKA oxidation test. Back in the 80s the test was run at 160C for 192 hours to discriminate between fluids in terms of oxidation resistance. In the 90s many fluid formulations had improved to the point where the severity of the test was too mild to show discrimination therefore the commonly used test temperature was raised to 170C. That has worked for just over 10 years but that is no longer the case. Fluids have improved even further and now in order to discriminate between 'good' fluids the test has to be run at 180C. Now, as a 'rule of thumb' each 10C increse in temperature halves the life of a fluid and of course the reverse is true. So I'm sure you will appriciate the implication as far as fluid life is concerned when we are discussing thermal stability.
I know this won't go down well with some people but I have in front of me two SAE papers. One is about the thermal stability of DEXRON-VI but also mentions 'synthetics'. It shows that 'synthetics' are not the magic answer that they used to be a couple of decades ago.
The other is about comparing the performance of various ATFs in a number of tests including oxidation and that too makes interesting reading, at least to me.
Have I made any useful contribution here? Please tell me if the answer is NO!

 

[Jim Allen]

YES! You always do!

Was waiting for you to chime in. I have seen those old ATF charts all over, including in some fairly recent Amsoil literature. I think it was a simple and useful way to express the principle of hi-temp oxidation. It just need an upgrade to reflect the current technology.

 

[Whitewolf]

Thanks Jim. I wasn't sure whether I was explaining what I was trying to say very well.
I think that you are correct that it needs updating but then I don't think that an updated version would support their point.

 

[Silber Igel]

Whitewolf, (Jim??? is it???)

Thanks!!! You are on target at answering my questions. I'm of similar opinion but without the data to make my case. Since the original data was developed and presented there's been quite a number of changes in automatic transmissions, not the least of which has been a slow but steady improvement in ATF formulations.

I've done the math, for those less empowered, to convert your Centigrade numbers to Fahrenheit to give a more familiar, to most, idea of the relative change in temperatures used in the tests over the last 30 years.

160 C = 320 F
170 C = 338 F
180 C = 356 F

Each 10 C is approximately an increase of 18 degrees F. Today's test is a rigorous requirement. For comparison.... 'deep frying' temperatures are 175 and 190 °C (345–375 °F).

Improved thermal stability, regardless whether or not the ATF is made of 'dino', synthetic, or grape juice, means that the modern ATF performs better and lasts longer given a well designed AFT cooling system without a 'supplementary' cooler. Hence the 100K mile change intervals for some vehicles. The caveat here, is that you have to comply with the manufacturer's recommended change intervals if you are going to do any towing.

 

[Silber Igel]

Dang!!!! I can't figure out how to insert an image here!!!!

Using Whitewolf's last posting and this link to a temperature/longevity chart that I posted as an example (similar to this one) .... http://www.tciauto.com/Products/TechInfo/trans_life_expectancy.asp

What we find is that the highest temperature on the chart, 315F (157C){where clutches and seals 'burn out, fluid turns to carbon, and, apparently Monkeys fly!!)is some 41 degrees F (20.2 C) below the current AFT testing requirement for thermal breakdown.

I'd say the charts need serious updating to reflect today's improved fluids. Any thoughts Gents???

 

[Jim Allen]

Originally Posted By: Whitewolf

I think that you are correct that it needs updating but then I don't think that an updated version would support their point.


I assume you mean that a synthetic is necessary as opposed to a dino. I agree, but the charts are still an indicator of how well the fluid hold up to high temps. I've seen 285 degrees a few times (measured at the cooler out line).

Here's a related question: Where do you think the best place to monitor trans temp? There are lots of schools of thought on this and all the arguments I've seen have some merit. Ultimately the the hot spots that will degrade the fluid but if it's cooled off quickly, then less harm is done, nez pas?

 

[Silber Igel]

The charts are .... to quote Field Marshal Bernard Montgomery, 1st Viscount Montgomery of Alamein ..."USELESS! BLOODY USELESS!!!!"

 

[Silber Igel]

Originally Posted By: Jim Allen
Originally Posted By: Whitewolf

I think that you are correct that it needs updating but then I don't think that an updated version would support their point.


I assume you mean that a synthetic is necessary as opposed to a dino. I agree, but the charts are still an indicator of how well the fluid hold up to high temps. I've seen 285 degrees a few times (measured at the cooler out line).

Here's a related question: Where do you think the best place to monitor trans temp? There are lots of schools of thought on this and all the arguments I've seen have some merit. Ultimately the the hot spots that will degrade the fluid but if it's cooled off quickly, then less harm is done, nez pas?


According to Whitewolf, 'dino' ATF fluids may perform as well as synthetics. We'll have to see is interpretation of the studies.

Yes! I should think they wouldn't support the sale of add-on coolers once you know that the 'testing' temperature is 'off their charts'.

The charts reflect something ... old ATF thermal breakdown, I guess. They are what they are. I'm not sure how that applies to new fluids since their data range isn't high enough to include the new test standard and there may not be a linear correlation between the old and new fluid performance across the temperature range. For example, the new fluids might be much more resistant to break down at lower temperatures, for example, than the old oils.

Where to place the temp probe.... a very interesting question. I'm not an expert in such things but my preference would be to put it in the sump for the reason you stated. Picking off a temperature at the transmission's fluid 'out' tube would give higher readings. Placed after the heat exchanger, it may give you lower readings. In the pan the oil's temperature would be a composite, or 'average' temperature, of the post heat exchanger fluid,'droppings & spray' from the internals; and heat from the metal parts enclosed by the pan and perhaps a better indicator of the oil's actual temperature. I found this on a site for aircraft engines... it would appear to validate using the sump as a measurement point.

" ... The best method of determining how hot the oil and how accurate the gauge is to take the oil's temperature. Immediately after landing use a long thermometer and dip the oil. We use a three foot mercury scientific thermometer and lower it into the oil filler tube. "

Anyway, I think that the absolute high temperature reading is not so important. A quick and temporary increase or decrease isn't so important. What I'd be looking for is a steady increase or decrease in the temperature beyond the 'average' observed temperatures. Frankly, the systems are so well dampened that the 'highs and lows' are probably irrelevant.

 

[Whitewolf]

Originally Posted By: Jim Allen
Originally Posted By: Whitewolf

I think that you are correct that it needs updating but then I don't think that an updated version would support their point.


Where do you think the best place to monitor trans temp? There are lots of schools of thought on this and all the arguments I've seen have some merit. Ultimately the the hot spots that will degrade the fluid but if it's cooled off quickly, then less harm is done, nez pas?


The best place to monitor the fluid temperature for extremes is torque converter out. That's where typically you see the highest temperatures.