Replaced factory RT1252 with RT1258 today

[Hellwig]

Results are fantastic. The ambient temperature is 78F today. The transmission working temp used to be 205F to 210F. Now it fluctuates from 176F to 180F when the vehicle runs on road. After the vehicle stops, tranny temp slowly spikes to 185F. The engine coolant working temp used to be from 190F to 195F with RT1252 (90.6 C/195F), and now it fluctuates from 176F to 181.4F with the new RT1258 (82C/180F).

I chose to do it in a local workshop with one and half hours labor charge plus negligible shop supplies and taxes. Coolant used for the replacement is way less than a gallon.

 

[SyndicateZ]

I need this

 

[Hellwig]

I need this

I honestly feel all gen 4 expeditions need RT1258 for the longevity of the 10R80 transmissions. I guess Ford adopted to RT1252 since model year 2022 is solely due to the EPA emission/mpg requirement, nothing else.

 

[Hellwig]

Tested it on a hilly local road today. Ambient temp is 70F. Road is very steep, and speed was under 20mph. Engine working temp is still 176F to 181.4F, but the transmission temperature stabled at 200F, and spiked to 210F very briefly for only once. Once getting back to highway, transmission temp dropped in between 190F to 195F.

 

[Dice Roll]

I can’t remember which one went in at the dealer when I had the coolant flushed. My temps are pretty close to yours except I havent seen 200 even when towing.

 

[Hellwig]

I can’t remember which one went in at the dealer when I had the coolant flushed. My temps are pretty close to yours except I havent seen 200 even when towing.

I was on a stop/go local road and it is very steep when it hit 210F for a few seconds.

 

[5280tunage]

What's interesting here is that it looks like that's rated for 180degrees, I have an SPD 180degree thermo sitting in my garage that's been in there for 4 years. I tried to get the dealership to put it in when I was getting a coolant flush and they wanted $800 to do it. Guess I should probably do it sometime on my own, if it helps the tranny run cooler. I don't need another new tranny.

 

[HILLY]

I'm in the south, so running 170*.

Definitely let's the tranny run cooler. I hardly ever get over 200*. Plus I've "deleted" the shutters which made a difference. I ran a scanner to track when they were open or closed and it was amazing how often they were shut unless running A/C full tilt on a hot summer day.

 

[Fastcar]

I've been reading this and wonder if anybody has replaced the trans pan with a deeper one. I ran into that years ago with a dodge truck plowing snow. You'd think that with cold temps in snow it wouldn't heat up but it did. Actually it ran hotter in reverse, could actual see the needle climb as I backed up. Anyway the extra quart or 2 of fluid made the difference.
Also where is the temp sensor located?

 

[5280tunage]

I've been reading this and wonder if anybody has replaced the trans pan with a deeper one. I ran into that years ago with a dodge truck plowing snow. You'd think that with cold temps in snow it wouldn't heat up but it did. Actually it ran hotter in reverse, could actual see the needle climb as I backed up. Anyway the extra quart or 2 of fluid made the difference.
Also where is the temp sensor located?

I looked into it but i don't have clearance with my skid plates to fit the deeper pan. PPE has one.

 

[Fastcar]

I guess I'm missing something. Or maybe I haven't messed around much with this recently. Seems that the approach is questionable. I'm in no way an engineer but.. You have how many quarts a trans holds, then you are trying to cool it in a container that is already trying to cool the engines coolant. It would seem to me that a larger transmission cooler and/or more fluid might be a better option. Also the skid plate may be preventing cooler air from cooling the trans pan, at the least it is holding heat. Another thought, could you remove the skid plate and cut vents or holes in it to direct air to the pan?

 

[5280tunage]

I guess I'm missing something. Or maybe I haven't messed around much with this recently. Seems that the approach is questionable. I'm in no way an engineer but.. You have how many quarts a trans holds, then you are trying to cool it in a container that is already trying to cool the engines coolant. It would seem to me that a larger transmission cooler and/or more fluid might be a better option. Also the skid plate may be preventing cooler air from cooling the trans pan, at the least it is holding heat. Another thought, could you remove the skid plate and cut vents or holes in it to direct air to the pan?

If you're referring to mine, there are already vents along leading services to allow air in and out. But also, thermally speaking, one way to look at it is that the skid plate could be trapping heat, but I actually believe it would work a lot more like a large heatsink. It's a huge, heavy piece of metal that could actually draw some heat away. The PPE larger capacity pan actually has veins on it, which function a heck of a lot better than the plastic piece of junk under there. I'm sure that would help a lot.

and even the tiny heat exchanger in the front of the tranny is blocked by so many things, I have a feeling there is very little airflow actually hitting that thing. And you're right, I would think a larger tranny cooler would make a big difference. the whole point of this thread was that the lowered operating temp. thermostat helps everything run a bit cooler.

 

[TX-EXPMAX]

I swapped whatever was in my 2019 with the RT1252 a couple years ago and it dropped my temps similar to what you're seeing now as well. I only touch 200 when it's really hot outside and i'm in stop and go traffic or running it hard. Otherwise, I hang in the 180-195 range...wonder if this newer one you're referring to is even better?

 

[Hellwig]

I swapped whatever was in my 2019 with the RT1252 a couple years ago and it dropped my temps similar to what you're seeing now as well. I only touch 200 when it's really hot outside and i'm in stop and go traffic or running it hard. Otherwise, I hang in the 180-195 range...wonder if this newer one you're referring to is even better?

RT1252 opens at 195F, and RT1258 opens at 180F theoretically (176F in reality). My vehicle came with RT1252 from factory and the transmission operating temp used to be 205F to 210F. When towing a 4000 lbs trailer, the operating temp was 215F. It seems the new RT1258 on my vehicle works same as the RT1252 on your vehicle.

 

[LG_123]

What are you using to measure temperatures?

Ours warns me when we get over 228F in the engine, which happens occasionally when towing ann 8,000# travel trailer uphill, especially when the oil is a couple thousand miles old.

Our transmission almost never gets to the point where the car gives me a number because it’s over.

But I can’t see temperatures otherwise when it’s in the normal range.

This is a 2019 expedition.

 

[GlennSullivan]

I have a 2017 3.5 / 6 speed. I don't experience trans temp over 200 during normal driving and 205 when towing a 6500 lb car/trailer combo. should I consider this new thermostat to lower operating temps even more?

 

[iowacarpenter]

I have a 2017 3.5 / 6 speed. I don't experience trans temp over 200 during normal driving and 205 when towing a 6500 lb car/trailer combo. should I consider this new thermostat to lower operating temps even more?

I am curious as well. Does this other thermostat work in the 15-17 trucks?

 

[T Bird]

Temps in my 2015 Expy EL Limited are 195-198 engine and 200-205 tranny. Tranny goes to around 220-225 pulling 6000# trailer, which I understand from what I read here is ok, but it's a little higher than I like. Thought about adding a tranny cooler, but maybe a RT1258 is all I need. What do you think?

 

[Hellwig]

Temps in my 2015 Expy EL Limited are 195-198 engine and 200-205 tranny. Tranny goes to around 220-225 pulling 6000# trailer, which I understand from what I read here is ok, but it's a little higher than I like. Thought about adding a tranny cooler, but maybe a RT1258 is all I need. What do you think?

I would try RT1258 firstly, coz it's a much easier and cheaper option. And it doesn't have any side effect, anyway.

 

[cbphotoguy1]

Hey guys I also have temperature concerns when towing. Last very hot day towing my 6500 lb trailer up a big hill i heard and felt a big loud clunk, got a wrench symbol on dash, scared the crap out of me - I slowed down and road levelled off and temp cooled back down without further concerns. My dealer said i was pushing it too hard but I suspect a faulty thermostat overheating the tranny but when researching replacing RT1252 all sites indicate the RT1258 will not fit my 2020 Max Expo. Is the Motorcraft part RT1252 now updated ? Any feedback would be appreciated.