2000 F250 4WD CCSB. Just had fluid/filter changed this week (synthetic) due to it overheating/puking fluid last Sunday pulling my rockcrawler. Torque app is reading 190+ and fluid is venting......again. Temps here are mid to upper 90's, index 110. Cooler is stock so I need a 6.0 cooler upgrade. Afraid to drive it in this heat. Fire ext is ready at all times. Anyone else who has not done the 6.0 upgrade have trans temps like this in the heat? Curious if this is a pre cursor to bigger issues. Trans shifts fine, no slippage, nothing out of the ordinary, just won't stay cool.


EDIT:

Looks like this is my problem

 

Normal temps are about 100F over ambient. 190F on a 90F day (heat index is meaningless to a truck) is absolutely normal.

 

When the Torque app is reading 190 deg where is that reading taken?
Is that temp the hottest the fluid gets?
If trans fluid temp is say 100 deg going back to the trans after the coolers what would be a normal temp rise in the trans?
Ford's idea of "normal" trans fluid temps is from 50-230 deg as the dash gauge will read mid scale for that range of temps.

 

I've driven over 1200 miles in the past couple of weeks with my camper on the truck and atv trailer behind. On flat stretches, in 90-100 degree temps, my tranny fluid temp (monitored via Torque app) was 190-195. Your readings are perfectly inline with mine. But my fluid isn't "venting".

On a 5 mile climb of 5-6 percent grade, driving into a stiff headwind, 2nd gear, 4000 rpm, 65 mph, tranny temp reached 230 and stayed there until the road leveled off. And then it dropped back to 195 or so. Normal.

I just changed the fluid and filter before all of the above.

 

So at 195 deg the radiator trans fluid cooler is not doing anything because the engine coolant thermostat opens at 195 deg. When the trans gets to 230 deg it is heating the engine coolant. What are engine temps when that happens?

 

According to Mark K the trans fluid is not heating the coolant. Here is one of the places he explains it:

https://www.ford-trucks.com/forums/1...r-input-2.html

 

Wrong.

The engine thermostat does open at 195, but that's not the temperature of the coolant where the trans cooler is located. The radiator cools the coolant. That's why there is a radiator. So now that the coolant is colder than the thermostat temperature it can cool the trans fluid.

The ATF is always heating the engine coolant. That's why there is a transmission cooler inside the radiator.

 

So....on a day with temps in the 70's...pulling my 5th wheel....trans temp gauge says...180-185 on flat ground but goes to around 200-205 pulling a long hill....is this normal??

 

Normal to excellent.

 

So what temperature is "too high"?

And where do the temp readings come from? Is there a factory sensor? Where is it?

(Hoping you'll answer in regards to OP, AND my truck: 07 E350 v10 with 5speed automatic Mercon SP)

 

Oops, I forgot about the temp drop through engine coolant radiator. So that part is wrong.
The point was when the trans temps get up to 235 deg this must be putting a load on the engine radiator cooling. Wouldn't it be best to keep the max trans temps around 190?

I'm confused - if the trans fluid is being cooled isn't the engine coolant being heated?

 

It would be best to keep trans temps around 190, but that's not always possible. And the radiator is sized to reject the heat from the engine along with the trans heat.

I said that the engine coolant never heats the ATF. I never spelled it out, but the ATF obviously does heat the engine coolant.

Too high is over 250F. If it reaches 250F find a safe place to stop. Idle, or even better, fast idle in park or neutral until the temp comes down. DO NOT SHUT THE ENGINE OFF WHEN THE TRANS IS OVERHEATED. That will cook it.

The factory sensor for both the 4R100 and the 5R110 is on the solenoid body. That's inside the pan.

 

It's done with engine coolant.
A properly sized cooler and a thermostat could keep the trans fluid temps close to optimum.
It boils down to cost.

 

I have done the 6.0 cooler upgrade and I am still having the issue of overheating. It only happens on steep winding roads traveling less than 35 mph. I am at a loss of what to do next!

 

Not what I want to hear. I have a 6.0 cooler, arrived this week, awaiting install.