I recently purchased a ScanGuage II and installed it in our '09 F-250 SD 5.4 slush-a-matic with 4.30's and 31 1/2" tires. This unit is primarily used for towing and I wanted to keep an eye on the trans fluid temp. By the way, I really like the ScanGuage II. It gives me real time fuel mileage, coolant temp and accurate trans fluid temp, among many other things.

My question for you guys that pull your trucks hard on a regular basis is this, what is the maximum trans fluid temp that I should allow the slush-a-matic to rise to? I towed our 9000# 5ver 200 miles one way to Indy for the 500 over Memorial Day weekend and the highest TFT was around 180 to 185 max. It was under 180 most of the time.

What are the upper parameters of TFT that his tranny will endure and still live a long trouble free life?

Thanks guys.

 

Those temps are perfect. The warmest I would go with mine is 240 after that you should start thinking about letting her cool down..

 

It can run all day long at 220°F with no problems. You can go as high as 250°F for up to a half hour at a time. If you need to cool it down idle or fast idle in park or neutral. Don't shut it off when it's really hot or you can cause damage.

 

I like to see below 225 myself. In moderate temps mine is staying around 165 which thrills me. Watch for the average over time. Will get hotter as it wears. Does that until the heat takes over and ends the trans. My 98 F150 was used hard and struggled to keep below 200 and easily found 250 if not paying attention and driving accordingly.

 

Thanks again guys!

 

this makes me feel great!! i have towed 12k + for 4 hours one way and never saw over 190 f... most of the time mine is at 160-175

 

I don't know why that would be true. What does happen over time is that the coolers get plugged. The oil side can collect debris from the trans, and even more important the outside of the cooler can collect all sorts of debris which restricts the airflow over the cooler.

 

I don't mean to sound confrontational, but there isn't an ounce of truth to this. Both yours as well as the OP's transmission temperatures are regulated by a thermostat.

The transmission temperature has everything to do with operating conditions and the functionality of the cooling system. Normal wear has nothing to do with it, and lots of things can break without the transmission ever overheating.

 

I agree.

X2

 

Mine averages 140-150 while unloaded according to my Isspro gauge with the sensor in the spot beside the transmission pan, does that seem low?

 

hmmm, Well I will agree there is much more to health than just temp. Kinda hard to write the book on trans status in a post. lol There are always hard parts that can fail. Many have grenade'd a fresh good trans with HP. But I will stand by a couple things regarding temp analysis.
1- clutches wear and slip. Heat is created. This is not always instant and will show in temp.
2- Worn bushings and overall trans wear will degrade the efficiency of the trans. HP in that is absorbed and not sent out the tail WILL increase the heat in the trans.
3- the stat can only modulate temp when cold. Has no ability to help cool once fully opened. As the heat generated overtakes the cooling system the trans WILL run hotter.
4- not all trans have stats and my reference to the 98 was one that does not.
5 - it is well spoken of that higher temps shorten trans life. Been that way for decades....
As a side note , it matters greatly where the temp is measured. Most like it in the pan. (Factory essentially is) It will not show these symptoms as well as if monitoring trans output to the cooler. Big three customers don't like to see the temp rise and falls so much. (obvious by the dash idiot gauges we all are stuck with) The direct clutch slipping in the 5r110 don't show temp because of this.

So in short I can see your point that you the user will not really catch the clutch failures unless they know their machine and what to look for. . The temp rise is not linear and many smaller failures will not show with the cooling system these SDs have.

Based on your comments you could brake torque (old term) the truck until the cows come home and never blow it because the heat does not matter. I would have to dig it up but have a vid of a older trans taking temp from 100 to +300 deg in about 5 seconds due to a loose converter installed. Trans was fine and healthy. But if I kept it there I cannot believe it would last. Maybe you guys have better luck than some of us. I read about direct clutch failure that tell otherwise because they can't just replace the solenoid that cause it and drive another 200k. hmmm

OP
Good point is made that there is more to evaluate than just temp. I hope I did not steer you wrong and think your temps are good.

 

Schmidt. It is not unreasonable. I know mine is similar unloaded, and have read of others in that range. Outside temp is also a factor. These trucks were designed to haul so struggle to make temp when not working. Trans don't have fuel contamination like the engine in particular and the trans fluid is designed to adsorb a percentage of water. Occasional work up to temp is always good. Though not practical for some.