Transmission temperatures

[max78]

I don’t see this being the reason. The thermostat could be working properly but the fluid could be retaining heat differently, or the system could no longer be dissipating heat the same, or the trans could be building heat more than it used to.

In all of those, the fluid temp could rise with the thermostat working as it should. And that doesn’t explain why the temps would reach highs it didn’t before, with a good working stat. If the stat was only opening later (say 4 degrees), the fluid and cooler should still cool it down to what it was if they are all operating the same.

It seems more likely some combination of fluid quantity (esp since that is difficult to measure) and efficiency in the trans cooling (200k worth of bent fins hindering air flow).

A failing thermostat that's not opening all the way will do exactly that. The thermostat is designed to open at a specific temperature so if your gauge is seeing 205 your thermostat is also seeing that same 205.

Other causes could be more slipping could be happening due to the clean fluid, that could be generating more heat. Reason why is when you drain old fluid it has a small amount of worn friction material suspended in there helping the trans grab, the new fluid does not have this so you get a little more slip. Try an adaptive trans relearn to see if it makes any improvements. Remember all these modern vehicles slip the locked up torque converter about 50 rpm at "full" lock, that's why I tuned my Fusion and will my new Expy.


On the old 200k mile trans they say leave it if you never changed it because that suspended fluid is your friction material now.

 

[Linksvu]

A failing thermostat that's not opening all the way will do exactly that. The thermostat is designed to open at a specific temperature so if your gauge is seeing 205 your thermostat is also seeing that same 205.

Other causes could be more slipping could be happening due to the clean fluid, that could be generating more heat. Reason why is when you drain old fluid it has a small amount of worn friction material suspended in there helping the trans grab, the new fluid does not have this so you get a little more slip. Try an adaptive trans relearn to see if it makes any improvements. Remember all these modern vehicles slip the locked up torque converter about 50 rpm at "full" lock, that's why I tuned my Fusion and will my new Expy.


On the old 200k mile trans they say leave it if you never changed it because that suspended fluid is your friction material now.

Good point. I didn’t think about it only partially opening and hindering flow. I’ll have to look into what it would take to replace that thermostat. Might be worth it on the next fluid change.

 

[max78]

Good point. I didn’t think about it only partially opening and hindering flow. I’ll have to look into what it would take to replace that thermostat. Might be worth it on the next fluid change.

You have to drop the valve body and it just slides right out, not a hard job really.

Ford Ranger 6R80 Thermal Valve ByPass Cooler Mazda BT50 6R80 Thermal Bypass Valve Location Leadframe

Ford Ranger 6R80 6R60 Valve Body Removal & 6R80 Thermal Cooler Bypass Valve & 6R60 Thermal Cooler Bypass Valve, Transmission Thermostatic Cooler Bypass Valve...

www.youtube.com

 

[danimerciss22]

It’s a known problem in the F150 world. My bet is that the filter and fluid got changed, but nobody did anything with that thermostat inside the 6R80 which restricts the oil flow to the oil cooler. There is a thermostat bypass one can buy.