Do these tables still apply with synthetic fluids?

[ecco123]

You know there are some others like these.

I mean, do these temperature lifespans apply with synthetic fluids, or even with modern fluids?

I guess, since these tables are easily found on transmission cooler manufacturers that are interested in giving you the worst perspective, that they are valid for old fashion Dexron II or so, but modern fluids would take much more temperature without problems.

Or maybe I'm wrong?


Also, when they say, for example, a transmission will last 25000 miles at 240ºF, it means at a mantained temperature during that 25000 miles, so a peak temperature of 240ºC for let's say a minute won't affect much, will it?

 

[gathermewool]

Quote:
240C
for a minute means you've probably got other issues

On a serious note I think this type of thing is like other oils trying to outperform each other in wear tests or sludge clean up tests. One test or rule of thumb won't necessarily carry over into the real world.

 

[CourierDriver]

lubegard.com has some tables,,,heat is the no.1 killer on trannys they say.

 

[CharlieJ]

I always read that heat is the number 1 killers of transmissions but I would have figured that never changing the fluid would be the main reason for trans failures.

 

[d00df00d]

What transmission will ever hit >300 degrees?

 

[unDummy]

All it takes is some warm weather stop/go traffic driving. For those of you that see the 'beach traffic', or go thru city traffic, like NYC, high ATF temps are pretty common.

 

[Colt45ws]

Actually I find that my highest temps are on the freeway for some reason. I can get it to 170-180 in the city if I beat the [censored] out of it like its a cop car. But on the highway it will work up to 180 and hold right around there. If it needs to unlock the TC to climb a hill I have seen it hit 200.
This is pan temp too, so temp coming out of the trans to the cooler is probably quite a bit higher especially when its unlocked.

 

[d00df00d]

Didn't know that. Thanks for the info.

 

[Gary Allan]

Quote:
Also, when they say, for example, a transmission will last 25000 miles at 240ºF, it means at a mantained temperature during that 25000 miles, so a peak temperature of 240ºC for let's say a minute won't affect much, will it?


The concept is under TWA (time weighted average). Fluid oxidizes/fatigues/ages on that basis. Your fluid transitions through a bunch of temps in the cycle from the pan, through the converter ..through the cooler ..returning to lube/bathe the rotating parts ..draining back to the sump. Those temps are going to form a composite temp.

The pan temp is usually a good indicator of "thermal insult reserve" and would be as good a point as any to factor the mileage figures that are depicted in the illustration.

The upper extreme temps fatigue the materials in the trans.

ATF is a power transmission fluid with minor lubrication properties. Otherwise, it's mainly a coolant.

 

[mechtech2]

That chart is useful because it shows how heat will severely shorten the life of ATF.
But I do believe full synthetic fluid would fare better.

 

[deeter16317]

I don't think its the affect on the fluid that shortens life, but the affect on the seals, orings, etc...and fluid won't cure that.

 

[artificialist]

Originally Posted By: deeter16317
I don't think its the affect on the fluid that shortens life, but the affect on the seals, orings, etc...and fluid won't cure that.

+1
When I watched videos from Power Stroke Help on youtube, he said that at 220F, the clutch plates on PSD transmissions would fail.

http://www.youtube.com/v/0BRQTsTxu4s

 

[Colt45ws]

I looked it up and it looks like my car will set a P1783 Transmission over temperature if Pan fluid temperature exceeds 127C (270F). Im sure this is similar if not the same on other Fords.

 

[deeter16317]

Originally Posted By: Onmo'Eegusee
I looked it up and it looks like my car will set a P1783 Transmission over temperature if Pan fluid temperature exceeds 127C (270F). Im sure this is similar if not the same on other Fords.



I believe a lot of newer cars have some sort of trans temp CEL that illuminates if the temps get hot...but from what I have seen, the temps where those CELs pop are already too hot and the trans is probably already cooked. FWIW, I have two Subarus (among other things), one of which I have had offroad pretty hard, and have never seen that light pop other than the initial check when started.

In my 99 CTD (with an actual guage), the hottest was idling in traffic or creeping along loaded (crawling a deep slush covered hill created the hottest situation I ever encountered at 220*F) where the converter is sheering fluid. Most of the time I was a few degrees over ambient...once the converter locked, I ran about 125*F even on a hot summer day.

I think a synthetic fluid will last longer in a "hot" transmission, but its still the components affected by heat in the transmission that determine that particular trans's overall life.

 

[Colt45ws]

Originally Posted By: deeter16317
Originally Posted By: Onmo'Eegusee
I looked it up and it looks like my car will set a P1783 Transmission over temperature if Pan fluid temperature exceeds 127C (270F). Im sure this is similar if not the same on other Fords.



I believe a lot of newer cars have some sort of trans temp CEL that illuminates if the temps get hot...but from what I have seen, the temps where those CELs pop are already too hot and the trans is probably already cooked. FWIW, I have two Subarus (among other things), one of which I have had offroad pretty hard, and have never seen that light pop other than the initial check when started.

In my 99 CTD (with an actual guage), the hottest was idling in traffic or creeping along loaded (crawling a deep slush covered hill created the hottest situation I ever encountered at 220*F) where the converter is sheering fluid. Most of the time I was a few degrees over ambient...once the converter locked, I ran about 125*F even on a hot summer day.

I think a synthetic fluid will last longer in a "hot" transmission, but its still the components affected by heat in the transmission that determine that particular trans's overall life.

I agree. The synthetic fluid will last longer at the same temperatures, but at some point you start cooking the trans. When it gets to that point it wont matter what kind of fluid is in it.

 

[deeter16317]

Last summer I changed the radiator in my 97 Outback (my urban assault vehicle) and added an auxiliary trans cooler (small one) at the same time. Last Friday I drove my typical 50 mile commute home and checked the temperatures at the cooler using an IR thermometer.

Radiator coolant hose inlet (from engine) - 205*F

Transmission fluid results:

At the radiator inlet - 180*F

At radiator outlet - 180*F

At the cooler inlet - 175*F

At the cooler outlet - 158*F

This was immediately after stopping (car still running), and the fans were not on...so there is still a significant heat exchange with little to no airflow through the cooler. It also shows there is little cooling being done at/by the circuit within the radiator.

So a cooler would probably be more beneficial than synthetic fluid in this case and provide more bang for the buck overall.

 

[Gary Allan]

Quote:
It also shows there is little cooling being done at/by the circuit within the radiator.


I'd more say that it indicates that the outlet temp of the rad and the in and out of the trans cooler were coincidentally 180F at that time.

180F inlet temp to the engine results in 205F engine outlet temp. The trans temp remained unchanged.

 

[deeter16317]

Originally Posted By: Gary Allan
Quote:
It also shows there is little cooling being done at/by the circuit within the radiator.


I'd more say that it indicates that the outlet temp of the rad and the in and out of the trans cooler were coincidentally 180F at that time.




Are they oil to water, or oil to air radiators? I've seen both...didn't really pay attention to this one when I installed it.

 

[Gary Allan]

No ..what I'm saying is that in your case it might have appeared different if you had run around the block in 2nd gear before doing the shooting. The trans would probably be hotter and the fans may have indeed engaged and you would not see the 3 points of 180F.

180F is not an unlikely temp to see at the trans or the lower rad at that point in operation.

 

[deeter16317]

I guess I don't follow, I just come in from a 50 mile commute of which the last 3 miles were stop/go traffic? It wouldn't get much hotter (conditions) than what it was subjected to.

The point is, the cooler is doing a decent job of dropping the temp 20*F with no airflow...160*F is well below the better case scenario for trans fluid life.