8F35 - 8 Speed Transmission - Temperature/Cooling

[Cherokee]

All interesting stuff,
But like an engine the tranny should not be over cooled. Adding too large of a tranny cooler would not be wise.
Way way back on my 1988 4cylinder Tacoma I added I think it was a 10,000 btu tranny cooler in front of the radiator.

We could measure fluid temps then. We had a thermometer on a flat dip stick like wire that went in the dip stick tube. It was home made, yeah back then we did shit like that.

You old guys remember, we could tend to our own vehicles back then but people would overfill a tranny so they sealed em up.

In the Florida heat and humidity hauling medical surgery equipment. In heavy city traffic my tranny was burning fluid to brown in as little as 12,000 miles, we were driving 50,000 a year. My temps were 240-260
After the cooler was added I was back to 200-210. Very stable.
The fluid at 50,000 miles was still pink and smelled right.

BUT ! During the short Florida winter it did freeze now and then. If it was in the thirties or lower I’d cover the tranny intercooler up with card board.
My buddy did not do this, told me I was crazy, well I am but hey.

He didn’t listen to me even after I told him I consulted a transmission man. He put on a 16,000 btu cooler thinking bigger was better. Doing the same work as me in the same truck his temps fell to 180-185.
His oh so reliable transmission died on him in traffic at 80,000 miles. Might have been those cold mornings, ya think ?

Mine lasted until I sold the truck at 340,000 miles. A guy I knew bought it, used it as a maintenance truck for several apartment complexes, always loaded heavy with tools n such. Last time I saw him that Toyota was at 450,000 miles and running like new. Still on the original tranny.
The thermostat controlled intercooler makes perfect sense.

‘Tranny’ am i allowed to use that word ?
:’P

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[lsxmalibu]

Have to accept the cooler or heater we have....maybe change out the fluid for some good Amsoil and motor on.

 

[Tbone289]

The trans mounted cooler is basically a transmission fluid heater.
The transmission is never going to be cooler than the coolant temp....so why wouldn't ford program the engine cooling fan to come on at 185-190 to lower the coolant temp......which would lower the trans temp by at least 5 or 10 degrees....
Once your towing and the trans fluid temp is 210...220.....that little trans mounted exchanger with 200 degree coolant wont do anything

I never see coolant temperatures above 186 degrees, which will cool a transmission. With a 190 degree thermostat, why is your coolant temperature at 200 degrees? An engine that operates at 200 degrees must be supplied with coolant much cooler than operating temperature.

 

[Tbone289]

Have to accept the cooler or heater we have....maybe change out the fluid for some good Amsoil and motor on.

A supplemental transmission cooler can be added, so you don't have to just accept it if you're mechanically inclined.

 

[lsxmalibu]

I have a 7 year 100k mile warranty so I will do it after that......

 

[lsxmalibu]

I never see coolant temperatures above 186 degrees, which will cool a transmission. With a 190 degree thermostat, why is your coolant temperature at 200 degrees? Coolant sensors are usually near the thermostat, not at the coolest part of the cooling system.

My scanner shows 195 average with many 200 degree peaks...then back down to 195.

 

[Tbone289]

My scanner shows 195 average with many 200 degree peaks...then back down to 195.

OK, but again, that's operating coolant temperature at the thermostat, where the coolant is exiting the engine. I hope you realize that an engine operating at 200 degrees has to have coolant flowing through it that is much cooler than 200 degrees, otherwise it couldn't maintain that temperature... Your coolant temperature is reading at the hottest part of the system, not the coolest. The transmission cooler is fed from the coolest part of the loop.

 

[AVC]

Also note that modern Type III/IV synthetic fluids have smoke temps 30 to 70F higher than older Type I/II dino squeezins'.

 

[anthonym6]

I already did a drain/fill at 5k miles and plan to do it every 15k-20k if I tow as often as I did this year (2k miles of towing). The fluid is inexpensive on Rockauto and not difficult to change. Not losing any sleep over it, just thought it was interesting and its fun to share data with others.

 

[lsxmalibu]

Good info for sure. I think ford got rid of the 2nd cooler because trans temperature wasnt an issue .....would be cool to see numbers on how many maverick transmission failure were from heat

 

[r0tax]

The Car Scanner app has Cylinder Head Temperature which is the oil temperature from what I have read.

Thank you, I did previously find CHT in Forscan, I will add that one again.
I was thinking it was Coolant temp for some reason when I first found it.

 

[Tbone289]

Good info for sure. I think ford got rid of the 2nd cooler because trans temperature wasnt an issue .....would be cool to see numbers on how many maverick transmission failure were from heat

I suspect it's a combination of that and cost. It's cheaper to assemble one common cooling system among all 8F35s.

The problem is that transmission heat is directly correlated with the life expectancy of transmission fluid. Removing the supplemental Air to oil cooler and using the standard heat exchanger instead raises the average temperature of the fluid around 15 degrees. That's not necessarily a bad thing, as long as Ford recommends replacing the fluid more often in those Mavericks that are reaching higher temperatures, but I don't believe Ford's ATF maintenance recommendations have changed for 2025.

 

[Tbone289]

Also note that modern Type III/IV synthetic fluids have smoke temps 30 to 70F higher than older Type I/II dino squeezins'.

While that is true, using a higher-quality base stock doesn't necessarily improve the life expectancy of the additives, which also deplete due to heat and oxidation.

 

[lsxmalibu]

I suspect it's a combination of that and cost. It's cheaper to assemble one common cooling system among all 8F35s.

The problem is that transmission heat is directly correlated with the life expectancy of transmission fluid. Removing the supplemental Air to oil cooler and using the standard heat exchanger instead raises the average temperature of the fluid around 15 degrees. That's not necessarily a bad thing, as long as Ford recommends replacing the fluid more often in those Mavericks that are reaching higher temperatures, but I don't believe Ford's ATF maintenance recommendations have changed for 2025.

30k miles for the transmission fluid change if "Severe" service, such as towing

 

[Tbone289]

30k miles for the transmission fluid change if "Severe" service, such as towing

Is that documented by Ford? I've only seen 150K officially from Ford, which isn't even sufficient for normal duty. Hopefully 30K is official now in 2025 with the higher temperatures reached.

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