Transmission fluid temperature

[ShutterBugBev]

It was 102 in Albuquerque today and I noticed that my transmission fluid temperature was 193. I started doing research on it then came across an old thread here that you can no longer join. One of the posts stated that 270 degrees was the max you wanted to let it rise to - that seems awfully high. I have the new 2014 5.3L V8 Chevy Silverado and I'm so thankful I have the transmission fluid temperature gauge built in so I can monitor it. I'm not looking forward to pulling Raton pass in this heat but there's no other choice. Hope the transmission fluid temperature doesn't get too bad so I'm pulling over and stopping a lot. This heat this summer is just RIDICULOUS!!

[SKnight]

193 is fine. Concern starts, for me at least, around 225 and I don't want to see above 250.

At that point pull over, toss it in park and let it idle. The fluid keeps moving, the fan keeps spinning and it will cool things off far quicker than just turning it off.

Does yours have the auxiliary cooler? If not they're cheap insurance and can really do a job.

[golfmedik]

X2 on an auxiliary cooler hooked in series with the stock one, or replacing the stock one with a MUCH larger one.

[lbrjet]

193 is normal and tells you the truck is operating perfectly. As stated above you may want to pull over in the 225 plus range but be sure to keep the motor running. At 193 on a 102 degree day I highly doubt you will have a problem with your truck.


2010 F250 5.4L 3.73
2011 Flagstaff 831FKBSS
Equal-i-zer 4pt 12K

[acadianbob]

Don't know what temp the newer Chevy's typically run; but my F150 runs 195 normally. Can't believe that 193 is a problem.

[Jammer3025]

193 degrees is fine. I believe at around 230 deg it starts to break down. I seen 200 deg on a step grade last week in 90 deg wx, and I was going to pull over, but it went back down. If it does get up there, like it has already been said on here, pull over and put it in neutral until it cools down.

[ebemis]

I too have read MANY different threads on this thought and as a result tend to "monitor" my trans temps perhaps verging on the anal side down here in sunny MUGGY Florida. Mid 190's is my normal towing trans temps through the Central Florida "ridge" hills in the middle of a 90-95 degree day. When I pull off the interstate and don't have all that moving air, temps will climb to about 210 +/- until I get to a lower speed and things catch up. So I hope my experience adds to all the other comments here that it seems your temps are more or less in spec and no need to worry.

[Bryce]

There's a former Ford Transmission Engineer on some of the Ford Forums. His take is that modern transmissions and fluids are fine up to 220F all day long and up to 250F for short times (up to 1/2 hr).

Modern transmissions are thermostatically controlled and are set to run at a specific operating range. This is done for fuel mileage (warmer fluid is thinner and easier to pump around... Less drag).

Now on my old school transmission, it's not thermostatically controlled, and I have a large cooler (one from a 6.0L truck). It runs 50-60F over ambient temps unloaded and pulling my TT, It gets to 70-80 over ambient pulling my TT in the hills. I haven't pulled a steep grade with it yet. I'm more concerned that I'm not getting it hot enough in the winter now and possibly causing damage being too cool.

[joshuajim]

You have to remember that in most trucks the fluid runs through the aux cooler first and then the radiator cooler. The radiator will actually heat the trans fluid if it is too cold. This is designed that way to reduce the stress on the tranny on very cold days. Too cold fluid is just as bad as too warm. Considering that the radiator runs at 195 to 205 degrees normally, the 193 degree temp is about as low as it will go on a warm day.

[Bryce]

Originally Posted by joshuajim

You have to remember that in most trucks the fluid runs through the aux cooler first and then the radiator cooler. The radiator will actually heat the trans fluid if it is too cold. This is designed that way to reduce the stress on the tranny on very cold days. Too cold fluid is just as bad as too warm. Considering that the radiator runs at 195 to 205 degrees normally, the 193 degree temp is about as low as it will go on a warm day.

That transmission engineer I mentioned will argue this. His teams findings were that the cooler run through the radiator is at a spot in the radiator where the coolant is significantly cooler than the engine temps.... It's at the bottom where the coolant has been as cool as it gets. As a result, there no heating of the transmission fluid from the radiator, ever.

[DDC]

You Chevy will give you an audible warning if the temp gets to a certain point, the DIC will then instruct you to stop and let the engine idle.

[joshuajim]

Originally Posted by Bryce

That transmission engineer I mentioned will argue this. His teams findings were that the cooler run through the radiator is at a spot in the radiator where the coolant is significantly cooler than the engine temps.... It's at the bottom where the coolant has been as cool as it gets. As a result, there no heating of the transmission fluid from the radiator, ever.

As the former owner/operator of a transmission shop, I believe that you mis-understood your friend. The radiator cooling lines run in the same coolant that the engine runs typically entering at the top of the radiator and exiting at the bottom. In any case, the coolant at the bottom of the radiator after the thermostat opens is never less that about 150 degrees, even on a cool day.

Yes I have cut open radiators that had leaking trans cooler lines to show customers why we had to replace the radiator.

How could that possibly NOT result in heating of the fluid?

[SKnight]

The truth, as always, is in the middle. Trans coolers are on the output or cold side of the radiator, but still see no less than 150* or so. Yes, your mileage will vary by vehicle and all and I'm sure there's a cooler installed on the inlet or hot side of something.

It's done that way to protect the trans from thermal shock among other things. It makes sure the trans runs under pretty consistent temps no matter what.

[Bryce]

Originally Posted by joshuajim

As the former owner/operator of a transmission shop, I believe that you mis-understood your friend. The radiator cooling lines run in the same coolant that the engine runs typically entering at the top of the radiator and exiting at the bottom. In any case, the coolant at the bottom of the radiator after the thermostat opens is never less that about 150 degrees, even on a cool day.

Yes I have cut open radiators that had leaking trans cooler lines to show customers why we had to replace the radiator.

How could that possibly NOT result in heating of the fluid?

Read the posts from Mark Kovalsky. In his testing for Ford, even in extreme temps, the transmission fluid always was colder coming out of the OTW cooler (radiator cooler) than it was going in.

Larger trans cooler + 3/8" lines, delete radiator cooler or no? - Diesel Forum - TheDieselStop.com

How do you know that? What measurements have you done? Or are you just assuming that the radiator is hot, so it must heat the ATF?

I will state it again. The radiator cooler NEVER warms the trans fluid. Ever. Period.

I have measured ATF temperatures in and out of the radiator cooler, in ambients as cold as -40°F. I never found a condition where the radiator warmed the ATF. Not even close. The ATF coming out of the radiator cooler was ALWAYS colder than when it went in.

[joshuajim]

I want some of whatever Mark is smoking.

[lbrjet]

Mark retired from Ford in the mid 2000's but I trust anything out of his mouth for trannys built when he was working. Newer Fords may work differently, hard to say. Anything he writes about is Ford only and doesn't apply to other brands.


2010 F250 5.4L 3.73
2011 Flagstaff 831FKBSS
Equal-i-zer 4pt 12K

[joshuajim]

Originally Posted by lbrjet

Mark retired from Ford in the mid 2000's but I trust anything out of his mouth for trannys built when he was working.

So what you are expounding is studies that have been done maybe 20, 30 or more years ago. That's about as relevant as a flintlock is to an AR15.

Fluid viscosities have become much thinner, engines run 15, 20 25 degrees hotter, fuel economy considerations have completely changed engineering requirements.

One of the great rules of the internet is that if you keep repeating the same old drivel long enough, it becomes the TRUTH.

Bring me some data from the last 5 years and I will reconsider my position.

[lbrjet]

The mid 2000's includes the tranny in my 2010 F250 so 20-30 years ago is a stretch. Unless you are/were a Ford engineer designing and testing transmissions consider that maybe he knows more than you.


2010 F250 5.4L 3.73
2011 Flagstaff 831FKBSS
Equal-i-zer 4pt 12K

[joshuajim]

Originally Posted by lbrjet

The mid 2000's includes the tranny in my 2010 F250 so 20-30 years ago is a stretch. Unless you are/were a Ford engineer designing and testing transmissions consider that maybe he knows more than you.

Ahhh so you KNOW that the test results you keep expounding were done on a 2010 F250...

Hmmm seems quite a stretch for anyone to believe that!

[Happy Vibe]

Joshuajim , we are still in th early 2000's 2014 is not even 1/4 of he way through. So i'm not sure were you get 20-30 years ago. Since you are not believing an expert can you please tell use how many years you have been designing and testing transmissions.