What is temp range for transmission fluid?

Hi,

Have a '07 Expy and have added a OBD bluetooth transmitter mated to the torque app on a tablet. One of the available features for the app is transmission fluid temperature.

Since I lost our old expy to transmission failure, It's important to me to not exceed the operating range of this one. Can anyone tell me the temperature range of the transmission in this truck? If I'm towing and it starts to push the limits, I'd like to know and back off until it cools down.

Thank you

We teach the upper limit is 180 degrees F. regardless of the fluid type. The synthetic fluid is said to withstand higher temps but no one says anything about the seals withstanding the higher temps.
One of the aftermarket trans cooler companies has a chart comparing temp to life expectancy. When I find it I will post it as a sticky.

There's a transmission engineer over on Ford-trucks.com that claims over 200*F is not harmful and hotter can be run for short periods of time.

Is it ok for my trans to run cool? - Ford Truck Enthusiasts Forums

According to the 6R80 service manual, normal operating temperature for the 6R80 is 193ºF-215ºF. I'm not sure if the 6R75 has the same range, but the specs for the 6R80 are within the normal range for transmissions in general so I would imagine so. You're never going to be able to keep it under 180ºF while towing. Heck, you won't be able to keep it under 180ºF with the truck empty if doing 80mph on a moderately warm day.

Not to get into a battle here but take a look at what the link implies about trans temp and trans life.

Transmission Temperature Gauge: A Brief Guide - Transmission Repair Guy

Yes you can run the trans at a higher temp but what is the cost? The OEM's don't want you to know about trans temps, they are also in the repair business at $4000+ a pop.

mine runs right at 100 over ambient
today it was 194 and the outside was 92-96 depending on the accuweather folks on my phone.
i watch trans temp as a habit.
my big bus runs much cooler..165 to 180

stamp11127 said:

Not to get into a battle here but take a look at what the link implies about trans temp and trans life.

Transmission Temperature Gauge: A Brief Guide - Transmission Repair Guy

Yes you can run the trans at a higher temp but what is the cost? The OEM's don't want you to know about trans temps, they are also in the repair business at $4000+ a pop.

Click to expand...

There's no argument that cooler is better, but there's just no way you're keeping the 6R80 or 6R75 under 180ºF while hauling a trailer or even blazing down the highway empty on a summer day. You can easily keep them around 140ºF while driving around town, but even without a load they hover near 200ºF at high speeds on a warm day - and that's with an auxiliary cooler.

Yes you can but it would require a very large or thick trans cooler / fan setup possibly & a heat exchanger to dump excess heat into the engine's cooling system along with extra fluid capacity for the transmission. A system like that isn't cheap. The $139.00 trans coolers are more appealing but unfortunately aren't always sized correctly for the application.

It is all a matter of heat transfer. Most people don't want to modify to that level until the trans rebuild bill comes in. Or they don't have the space available for what is needed to accomplish such a large temp drop.

Another thing that the manufacturers aren't telling the consumer is that they have reduced the pump pressures to the bare minimum to squeeze every mpg out of fuel they can. Running the trans pump at a higher pressure takes more energy (fuel). With reduced pressures you also have reduced flow - less fluid is going through the cooler than it did in the old days. This in turn keeps more heat in the trans.