Explorer swap /4R70W oil cooler

[Postalpal]

I know I saw some posts in the past but I’m wondering at what temp you would you be concerned enough to want to consider getting a trans cooler & what one did you go with , I also thought I read where someone mentioned replacing the fan clutch as well to help ?
5.0 Explorer motor & 4R70W
Thank you

 

[bronco italiano]

Trans temps as low as possible. I don't use my radiator, I use an atomic cool with thermostat at 180 degrees

 

[fordguy]

Trans temps as low as possible. I don't use my radiator, I use an atomic cool with thermostat at 180 degrees

Same here.

 

[Bruners4]

I originally installed the stock Explorer transmission cooler after the in-radiator cooler just like a stock Explorer. Used Explorer cooler started leaking and I replaced it with a Derale 33604. Also running a Derale 13223 power steering cooler.

 

[66broncoCT]

I have mine running through the radiator and then the stock explorer fluid to air cooler. Will probably replace it with something bigger if it ever needs replacing but I figured it worked in the explorer it’ll work in the bronco.

 

[Broncobowsher]

I don't go with cold as possible. Proper operating temp is better. But what is that temp? I'll call it about 150°F. With a very broad 'about' in that.
It does need to warm up so it flows correctly. Clutches can be hurt with too cold of a fluid, shifts don't happen right, extra drag. A bit of heat helps drive out moisture. All good things. You can still get over 100k of trans fluid life.

It when you sustain over 200 that there are problems. And that is a sustain, not a random spike three times a year that comes down quickly. if it is the middle of summer and I cruise at 170, fine. No need to obsess over it. Any idea what the engine oil temp is? How about the rear end temp?

 

[904Bronco]

I look for 150* as a happy spot, my temp sender is in the pan. Too cool is bad, and higher temps (200*) are not good. As Broncobowsher says above, there is a range.

Some kind of cooler is needed, size and style will matter. My current build has a US Radiator with a trans cooler in it, I also have an Aux stacked plate cooler in line with it.

If you have an Aux cooler, it needs air flow (front of Rad) , but it also needs some form of protection from errant rocks. I have a story, so that is why i mention it

 

[Broncobowsher]

Since 904 mentioned pan temp, I'll go off on that tangent a little bit. That is the correct place to watch trans fluid temps. That is where Ford put the trans fluid temp in the 4R70W. That is where every OEM I know of has the fluid temp. Testing for OEMs, it was always the pan temp that was the one that mattered.

Not the cooler out or the cooler in temp. We would do those to see how good the cooling package was, but that wasn't the trans fluid temp that the logic cared about. Cooler out (out to the cooler) will always run hot. That is fluid leaving the torque convertor. If it isn't hot, thats because the convertor has been running locked up. It will always give you a false sense that the transmission is running too hot. The cooler return is also a bad place to watch temps. That would be like trying to watch engine temp by watching what the water temp is going into the engine. If you have a good cooler, but a mostly pinched line, the fluid will flow slow, dump all the heat and return nice and cold. But just a tiny bit of flow with hot oil cooking in the transmission trying to get through the cooler. While the cooler lines are an easy spot to tap a cooler sender, it won't give meaningful temps. The industry has set pan temp as the standard location, all the reference material on how hot transmissions run is based on pan temp.

The only usable in line temp sensor I can think of is for an electric fan. Put a temp switch on the return line. If you start pushing hot oil through the cooler because you lack airflow, turn a booster fan on. When the oil starts returning cold enough, turn it off.

 

[Postalpal]

I’m right around 200 degrees and have no problem installing one. It can’t hurt , so obviously right now I have the 2 lines ran from the 4R70W to the 2 ports on the aluminum radiator, how have some of you routed the lines when you add the cooler ? And what cooler have you been happy with ? Seems mounting it on the radiator support is pretty common

 

[Postalpal]

Would this be the idea way to route the lines ?

 

[Broncobowsher]

i would swap the ports on the transmission. I recall the fluid leaves the bottom port. I would run that to the oil to air cooler first. Then run that through the radiator.

Except---If you have one of the reverse flow radiator that puts the trans cooler on the hot side of the radiator. Then run what you show.

 

[Postalpal]

I will check. But I’m pretty sure I’m running this radiator

 

[Broncobowsher]

That is the reverse flow. Your original diagram is correct.
Traditionally the transmission cooler is on the cold tank (water pump side) of the radiator. The cools the transmission fluid in the coldest water in the cooling system.
That radiator they swapped the inlet and outlet sides, but kept the transmission cooler on the same side. Now the transmission cooler is in the hottest coolant, what comes out of the upper radiator hose. You will get transmission fluid coming out as hot as the engine coolant. This works fine when really abusing the torque convertor at low speeds as the trans fluid can flash to higher than coolant temps. But generally too hot for most peoples liking of transmission temps. Put a large oil to air cooler after the in radiator and you will never see trans temps hotter than engine temps even in the worst of times. The oil to air cooler will be running a pretty much fixed inlet oil temp of engine coolant temp. So enough cooler to drop the fluid temp ~30 degrees and you are set.
I'm not against using the in radiator cooler, or warmer. It will at least give a fixed starting point for the cooler to work off of.

 

[904Bronco]

This is the biggest cooler that I have been able to fit, and it is a tight fit. The grill will come on and off a few times to ensure that you clearance everything.

And there has been discussion on is the most optimum way to mount the cooler with the inlet/outlet pointing down. But many here have noted that this is how the Manufacturers have done it on numerous vehicles. I am using the Factory Radiator cooler first and then the Aux cooler.
There are smaller units available...
I run metal lines, as in I bend my own, and I minimize the use of hose as much as possible.

I hope this helps...

Summit Racing

2/11/25

Hayden transmission cooler with an fittings

HAD-689

$ 78.99

 

[lars]

This is the biggest cooler that I have been able to fit, and it is a tight fit. The grill will come on and off a few times to ensure that you clearance everything.

And there has been discussion on is the most optimum way to mount the cooler with the inlet/outlet pointing down. But many here have noted that this is how the Manufacturers have done it on numerous vehicles. I am using the Factory Radiator cooler first and then the Aux cooler.
There are smaller units available...
I run metal lines, as in I bend my own, and I minimize the use of hose as much as possible.

I hope this helps...

Summit Racing

2/11/25

Hayden transmission cooler with an fittings

HAD-689

$ 78.99

Mine's bigger, Doug

This took some doing. Wish the rest of my Bronco looked 1/10 as nice as yours. This was done after previously using a Long cooler similar to what you show, and finding it to be inadequate on what was arguably a fairly extreme trip, with all the bonus heat to absorb from the torque of my engine. It's a Mishimoto off Amazon.
https://a.co/d/09b92dO5 Flex lines transition to hard lines just behind the core support. Using Teflon with stainless overbraid hose was overkill but I had all the parts on hand. And as you can see I followed the Ford Way with port orientation.

 

[ntsqd]

Years ago I did some research on trans operating temperature and what I found was that the coolest it should operate at needs to be warm enough to drive any moisture (condensation) out of the fluid. A little more poking around lead me to roughly 160°, so that's what I've been looking for myself and advising.

Several years earlier than that I encountered an article in a auto trans rebuilder trade magazine that had a graph of trans life-span vs. operating temperature. At 180° it was decades. At something like 275° it was single digit minutes. I'm not sure if in the intervening years that has changed much, but it sure left an impression on me! Broncobowsher's numbers make me think that maybe not a lot has changed.

If the trans cooling system that you've put together normally runs cooler than 160° I'd say celebrate it, and then consider putting a thermostat in the system. They're sold by most of the online racing suppliers (Summit, Pegasus, etc.) and they typically start to open at 160° and reach fully open at 180° In really cold climates I wonder if the ATF ever does get warm enough? I've long advised putting the aux cooler first in the system so that the radiator has the opportunity to warm up the ATF in those conditions just before it goes back to the trans, but there are valid points about making it the last in the system.
For most people, who aren't driving to the Artic Circle or operating a tundra buggy, in practicality it doesn't seem to matter.

 

[Grey owl]

Years ago I did some research on trans operating temperature and what I found was that the coolest it should operate at needs to be

I know I saw some posts in the past but I’m wondering at what temp you would you be concerned enough to want to consider getting a trans cooler & what one did you go with , I also thought I read where someone mentioned replacing the fan clutch as well to help ?
5.0 Explorer motor & 4R70W
Thank you

warm enough to drive any moisture (condensation) out of the fluid. A little more poking around lead me to roughly 160°, so that's what I've been looking for myself and advising.

Several years earlier than that I encountered an article in a auto trans rebuilder trade magazine that had a graph of trans life-span vs. operating temperature. At 180° it was decades. At something like 275° it was single digit minutes. I'm not sure if in the intervening years that has changed much, but it sure left an impression on me! Broncobowsher's numbers make me think that maybe not a lot has changed.

If the trans cooling system that you've put together normally runs cooler than 160° I'd say celebrate it, and then consider putting a thermostat in the system. They're sold by most of the online racing suppliers (Summit, Pegasus, etc.) and they typically start to open at 160° and reach fully open at 180° In really cold climates I wonder if the ATF ever does get warm enough? I've long advised putting the aux cooler first in the system so that the radiator has the opportunity to warm up the ATF in those conditions just before it goes back to the trans, but there are valid points about making it the last in the system.
For most people, who aren't driving to the Artic Circle or operating a tundra buggy, in practicality it doesn't seem to matter.

Years ago I did some research on trans operating temperature and what I found was that the coolest it should operate at needs to be warm enough to drive any moisture (condensation) out of the fluid. A little more poking around lead me to roughly 160°, so that's what I've been looking for myself and advising.

Several years earlier than that I encountered an article in a auto trans rebuilder trade magazine that had a graph of trans life-span vs. operating temperature. At 180° it was decades. At something like 275° it was single digit minutes. I'm not sure if in the intervening years that has changed much, but it sure left an impression on me! Broncobowsher's numbers make me think that maybe not a lot has changed.

If the trans cooling system that you've put together normally runs cooler than 160° I'd say celebrate it, and then consider putting a thermostat in the system. They're sold by most of the online racing suppliers (Summit, Pegasus, etc.) and they typically start to open at 160° and reach fully open at 180° In really cold climates I wonder if the ATF ever does get warm enough? I've long advised putting the aux cooler first in the system so that the radiator has the opportunity to warm up the ATF in thosecool conditions just before it goes back to the trans, but there are valid points about making it the last in the system.
For most people, who aren't driving to the Artic Circle or operating a tundra buggy, in practicality it doesn't seem to matter.

Every situation is a little different, opinions will vary. I am in the maximum cooling camp, i would add a cooler and capacity if possible. I don’t think is such a thing as too cool for a transmission. Excessive heat hurts them, that said there are several options to keep the operating temps in check.

 

[ntsqd]

I used to be in that camp until an acquaintance who is one of those "in the know" local experts, he on auto trans', showed me a TH350 that had had excessive condensation in the fluid. How it was used and what it was out of I no longer know, if I ever did. The steels in the clutch packs had rust pits in them! Not huge, but not surface rust either. It was he who started me thinking about, and then researching the ideal minimum operating temperature. I understand that there is more to it than just the condensation, but beyond knowing that metals expand with temperature and that the trans designers likely had a minimum operating temperature target for setting the operating clearances I don't know more.
It was Billy's contention that while you can operate an auto trans stone cold there are two things that can or will happen. Excessive wear due to tight clearances was what he saw the most of, and those rust pits which weren't common but they did occur occasionally. His first thought seems very likely and reasonable, the second seemed implausible until I saw it.

There is no doubt that erring on the side of too cool is the better direction to lean.

 

[Broncobowsher]

Years ago I did some research on trans operating temperature and what I found was that the coolest it should operate at needs to be warm enough to drive any moisture (condensation) out of the fluid. A little more poking around lead me to roughly 160°, so that's what I've been looking for myself and advising.

Several years earlier than that I encountered an article in a auto trans rebuilder trade magazine that had a graph of trans life-span vs. operating temperature. At 180° it was decades. At something like 275° it was single digit minutes. I'm not sure if in the intervening years that has changed much, but it sure left an impression on me! Broncobowsher's numbers make me think that maybe not a lot has changed.

If the trans cooling system that you've put together normally runs cooler than 160° I'd say celebrate it, and then consider putting a thermostat in the system. They're sold by most of the online racing suppliers (Summit, Pegasus, etc.) and they typically start to open at 160° and reach fully open at 180° In really cold climates I wonder if the ATF ever does get warm enough? I've long advised putting the aux cooler first in the system so that the radiator has the opportunity to warm up the ATF in those conditions just before it goes back to the trans, but there are valid points about making it the last in the system.
For most people, who aren't driving to the Artic Circle or operating a tundra buggy, in practicality it doesn't seem to matter.

Nissan trucks run thermostats in the oil to air coolers. For 20+ years they have been built into the cooler itself. When hot they close forcing the oil through a double pass cooler. When open it is a bypass straight through the cooler without being forced through the cores. Really slick. Before that they had a little stand alone thermostat in the cooler lines, but that added 4 more hose clamps and all the extra hoses and mounting brackets. I have one of these coolers plumbed into my manual transmission.

 

[ntsqd]

Figured that I'd provide some links what I mentioned previously:
Summit Racing Oil Thermostat
Pegasus Racing Oil Thermostat
BAT-Mocal Oil Thermostat
Built into a filter pad, but spendy: Pegasus Racing Filter Pad but some like to put a spin-on filter in the trans cooling system.

I can see why in a production build where more hose clamps and hose barbs would be highly undesirable. They're not particularly welcome in a custom build (at least by me anyway), which is why I tend to use Push-Lock/Barb-tite type hose & hose ends for almost everything. But even at that it's still 4 more connections.