Right-oh! High temps at converter out are to be expected. But... they might not be all that relevant to the overall health of the transmission since those temps drop at the heat exchanger and after the fluid mixes in the sump.
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Heat and Transmission Failure Charts
- Thread starter Silber Igel
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Silber Igel
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I do....
Well I don't feel so bad about my 4L60 runing at 180-190F anymore after reading this post. Thanks! BTW, I heard GM is coming out with a dexron axle lube that is supposed to be real efficient for better CAFE. HAve you heard that?
Silber Igel
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Originally Posted By: Whitewolf
Sorry, I did not intend to appear to be blunt but it is a question that I am asked many times.
It's just like cooking, what temp and for how long?
No offense taken! Right you are... its just like cookin'!!!
Sorry, I did not intend to appear to be blunt but it is a question that I am asked many times.
It's just like cooking, what temp and for how long?
No offense taken! Right you are... its just like cookin'!!!
For what it's worth, I've worked on lots of industrial applications with automatic transmissions, assorted powershift transmissions, hydrostatic transmissions, and assorted hydraulic systems. In every application I can think of, the temperature sensor is ALWAYS installed at the hottest point in the system... which would be the 'out' port where oil exits the transmission and goes to the cooler. There are probably some obscure exceptions to this, but I can't think of any.
Same goes for engine cooling systems- the sensor is always mounted at the hottest point in the system- where the coolant exits the engine.
Same goes for engine cooling systems- the sensor is always mounted at the hottest point in the system- where the coolant exits the engine.
Originally Posted By: onion
In every application I can think of, the temperature sensor is ALWAYS installed at the hottest point in the system... which would be the 'out' port where oil exits the transmission and goes to the cooler. There are probably some obscure exceptions to this, but I can't think of any.
Me too, and I think that's the best place. As to sensor whre it isn't on the converter out port, I can name one that isn't, which is why I posed my question originally.
My Ford F150 4R75 has a built-in temp sensor and the manual says it's mounted up in the valve body. My Edge programmer can let me read that sensor and it appears to be running what I would call "normal" pan temps (about 160 degrees at 80 ambient with no load). The sensor input is used by the PCM to pull back torque when or if it thinks it's overheated. I don't know the actual number at which it cries "overheated."
In every application I can think of, the temperature sensor is ALWAYS installed at the hottest point in the system... which would be the 'out' port where oil exits the transmission and goes to the cooler. There are probably some obscure exceptions to this, but I can't think of any.
Me too, and I think that's the best place. As to sensor whre it isn't on the converter out port, I can name one that isn't, which is why I posed my question originally.
My Ford F150 4R75 has a built-in temp sensor and the manual says it's mounted up in the valve body. My Edge programmer can let me read that sensor and it appears to be running what I would call "normal" pan temps (about 160 degrees at 80 ambient with no load). The sensor input is used by the PCM to pull back torque when or if it thinks it's overheated. I don't know the actual number at which it cries "overheated."
Nice thread.
My new Silverado has run as high as 174F... no load, just a hot Texas day.
It is very 'neat' to be able to monitor the transmission temp.
Questions for WhiteWolf .... I do not find it chance that GM has allowed/enabled the transmission temperature montior while say oil temperature is not a concern.
1.) Am I correct in thinking this way?
2.) The owners manual clearly states to add more transmission fluid if required (leveraging the trans. temp. monitor and the dipstick as guides), should this be expected to happen and if so, why so with DEX VI vs. older fluid applications which never wanted us to even touch any part of the transmission fluid level?
Cheers
My new Silverado has run as high as 174F... no load, just a hot Texas day.
It is very 'neat' to be able to monitor the transmission temp.
Questions for WhiteWolf .... I do not find it chance that GM has allowed/enabled the transmission temperature montior while say oil temperature is not a concern.
1.) Am I correct in thinking this way?
2.) The owners manual clearly states to add more transmission fluid if required (leveraging the trans. temp. monitor and the dipstick as guides), should this be expected to happen and if so, why so with DEX VI vs. older fluid applications which never wanted us to even touch any part of the transmission fluid level?
Cheers
To be quite blunt, those charts are nothing more than a sales gimick. I've seen a plenty a trans run with stock cooling and at temps near 200*F for well over 200k miles.
Granted they had fluid changes, but the trans itself lasted just fine. Those charts don't take into account fluid changes IMO, like your supposed to leave the fluid in for the duration...
Granted they had fluid changes, but the trans itself lasted just fine. Those charts don't take into account fluid changes IMO, like your supposed to leave the fluid in for the duration...
I still feel better having a cooler and fairly recent fluid in my transmission. It rarely gets above 165. Strangely enough a few minutes of city driving made the temperature spike a lot faster than highway driving.
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Quote:
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?
It really doesn't matter then. If your school of thought is valid ...and I think that it is ..then no matter where you measure it you've got a good view.
Let's go with the hottest point out. Now we'll assume that you're reading it ..and you're seeing how long it stays there. If it stays there for a short time ..we don't worry. If it's there a prolonged time, we assume that it's fatiguing the fluid.
Can we agree, based on just about all of those charts, that there's a "time weighted average" do the degradation? That is, that the shortening of the fluid life is under "continuous" duty at that temp??
So I read the sump. I'm measuring "insult reserve" or buffering. You're reading peak ..or maximum insult amplitude and duration.
Is there really any effective difference?
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?
It really doesn't matter then. If your school of thought is valid ...and I think that it is ..then no matter where you measure it you've got a good view.
Let's go with the hottest point out. Now we'll assume that you're reading it ..and you're seeing how long it stays there. If it stays there for a short time ..we don't worry. If it's there a prolonged time, we assume that it's fatiguing the fluid.
Can we agree, based on just about all of those charts, that there's a "time weighted average" do the degradation? That is, that the shortening of the fluid life is under "continuous" duty at that temp??
So I read the sump. I'm measuring "insult reserve" or buffering. You're reading peak ..or maximum insult amplitude and duration.
Is there really any effective difference?
Originally Posted By: Gary Allan
It really doesn't matter then. If your school of thought is valid ...and I think that it is ..then no matter where you measure it you've got a good view.
Let's go with the hottest point out. Now we'll assume that you're reading it ..and you're seeing how long it stays there. If it stays there for a short time ..we don't worry. If it's there a prolonged time, we assume that it's fatiguing the fluid.
Can we agree, based on just about all of those charts, that there's a "time weighted average" do the degradation? That is, that the shortening of the fluid life is under "continuous" duty at that temp??
So I read the sump. I'm measuring "insult reserve" or buffering. You're reading peak ..or maximum insult amplitude and duration.
Is there really any effective difference?
Well said! And I agree 100 percent, Gary.
Any spot is a good spot to monitor, especially if you understand what may be happening elsewhere... e.g. running 250 in the pan equals "OMG" from the converter out.
A good way to educate yourself is to hook up several sensors with a rotary swx and monitor the temps under various conditions. I had an old diesel Blazer with sensors in the pan, cooler line out and cooler line in. That converter out line got scary to see sometimes! I ended up watching pan temps most often because I knew that the oil coming out of the converter was always going to be much hotter but that the pan was the "buffer," as Gary said. The pan is where the oil will spend the most "dwell" time at a specific temp. When I saw the pan at 200 plus, I knew the trans was getting hot!
It really doesn't matter then. If your school of thought is valid ...and I think that it is ..then no matter where you measure it you've got a good view.
Let's go with the hottest point out. Now we'll assume that you're reading it ..and you're seeing how long it stays there. If it stays there for a short time ..we don't worry. If it's there a prolonged time, we assume that it's fatiguing the fluid.
Can we agree, based on just about all of those charts, that there's a "time weighted average" do the degradation? That is, that the shortening of the fluid life is under "continuous" duty at that temp??
So I read the sump. I'm measuring "insult reserve" or buffering. You're reading peak ..or maximum insult amplitude and duration.
Is there really any effective difference?
Well said! And I agree 100 percent, Gary.
Any spot is a good spot to monitor, especially if you understand what may be happening elsewhere... e.g. running 250 in the pan equals "OMG" from the converter out.
A good way to educate yourself is to hook up several sensors with a rotary swx and monitor the temps under various conditions. I had an old diesel Blazer with sensors in the pan, cooler line out and cooler line in. That converter out line got scary to see sometimes! I ended up watching pan temps most often because I knew that the oil coming out of the converter was always going to be much hotter but that the pan was the "buffer," as Gary said. The pan is where the oil will spend the most "dwell" time at a specific temp. When I saw the pan at 200 plus, I knew the trans was getting hot!
Originally Posted By: 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???
Just because the fluid can survive that test dosen't mean components can. Normal seals are usually only good to around 225F. High temp seals are good to around 260 but live a lot longer at at cooler temp. All that test is saying is today's fluids typically last longer than the past. They are so good infact they had to raise the test criteria to get meaningful results on long life fluids. IMO.
That being said, the high temperature threshold for the hydraulic systems on the offroad equipment we produce is 200F. IMO stay at or below 200F and components will live a long and happy life with regualar fluid changes.
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???
Just because the fluid can survive that test dosen't mean components can. Normal seals are usually only good to around 225F. High temp seals are good to around 260 but live a lot longer at at cooler temp. All that test is saying is today's fluids typically last longer than the past. They are so good infact they had to raise the test criteria to get meaningful results on long life fluids. IMO.
That being said, the high temperature threshold for the hydraulic systems on the offroad equipment we produce is 200F. IMO stay at or below 200F and components will live a long and happy life with regualar fluid changes.
Originally Posted By: sciphi
I still feel better having a cooler and fairly recent fluid in my transmission. It rarely gets above 165. Strangely enough a few minutes of city driving made the temperature spike a lot faster than highway driving.
The reason it rises quicker in traffic is two fold...first you're not getting as much air flow at lower speeds, second the converter is unlocked and slipping in traffic which generates a ton of heat.
I still feel better having a cooler and fairly recent fluid in my transmission. It rarely gets above 165. Strangely enough a few minutes of city driving made the temperature spike a lot faster than highway driving.
The reason it rises quicker in traffic is two fold...first you're not getting as much air flow at lower speeds, second the converter is unlocked and slipping in traffic which generates a ton of heat.
I read all the posts about temp and so forth and now you ahve me worried. I have an 07 Grand Prix 20K miles with built in temp sensor and it runs 180* for about an hour but then after that it'll go to 205 and stay there esp on the last 12 hour trip to SC. 205* all the way there in 90+ degrees and AC on. Going up some mountains and converter unlocked it saw 230* for about 6 miles then came back to 205*.
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