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2nd Transmission Cooler


Elite Explorer
December 4, 2016
Reaction score
City, State
Fort Worth, TX
Year, Model & Trim Level
1997 5.0 4x4
Looking at relocating the factory cooler and adding an additional inline cooler. Need some opinions here.

I would like to relocate the factory cooler some where besides in front of the radiator. In doing so I am hoping to have that much less heat pushing through the radiator.

I would like to add an additional cooler also. Benefits are obvious.

What does anyone think about bypassing the radiator and just having 2 coolers inline with no inside the radiator cooler? My logic says that it would keep the radiator cooler?

And I do tow but nothing extreme. I am also more concerned about keeping things cool vs making sure the transmission is up to optimal temperature. I don't really live in a place that have 4 feet of snow on the ground 5 months out of the year.

Any thoughts/advice?

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I have a tube and fin cooler attached directly to the radiator face and a plate cooler where the OEM unit used to be. Its bigger than the OEM cooler. On top of the plate cooler I have a electric pusher fan to help cool when crawling. Its activated by a switch. I also bypassed the radiator pre-heater. The ports are 3/8 NPT pipe thread, so easy to get plugs.



I couldn't locate a picture of the pusher fan. The plate coolers work much better than the tube and fin types. They slow the fluid down so it can cool more. Bypassing the radiator dropped my transmission temps about 10 degrees, same when I use the fan at slower speeds. The OEM coolers work well and are very good quality. They need to be mounted in front of the radiator for air flow. Coolers do not work without air flowing through them.

I was looking at a tube and fun cooler to mount on the frame as soon as it comes out of the transmission. I think under there it would act more as a heat sink but should still help. I”m not against using something other than the stock cooler, just figured since I already have it might as well reuse it.

So you have electric fans that push air through just the trans cooler or went to an entirely electric fan set up?

Another thought I had was a tube and fin mounted on the back side of the skid pan. I have the RCI plate so if you could imagine that.

I also have the hood louvers on top that I thought about figuring out how to mount a plate style under the hood so as air exits it’s would run through the cooler also.

You can kinda see the hood vents and how I would mount them to the hood.



You are not going to get much of a drop in temp's unless it has air being forced through the coolers. I don't think all the work will be worth the gain. The really don't block the radiator since the air flows through them. I have the stock fan, but added a pusher fan to help air flow through the cooler at slower rock crawling speeds. I have the two trans coolers and a small power steering cooler mounted in front of my Explorer's radiator.
I found a couple of pictures of my radiator and coolers off my phone

I’d just add a second or larger cooler in front of the radiator. If a second large one was added, I’d consider bypassing the in radiator cooling. So much air comes through the grill at speed that the heat from the cooler isn’t a big deal. At crawling speeds it might come into play, but then you’d want a fan to cool it anyways.

A long frame rail cooler would have an effect as a lot of air pushes under these bricks.

Go with what is known to work well, I always say.

I also added a larger trans cooler & pusher fan directly to the face of the radiator. Changed up to an Alum Radiator, bypassed the trans tanks, and I am in an area that gets cold winters.

The trans will warm up faster than you think, and the warming tanks are protocol safety redundancy for the most part. If you live in the frozen tundra (also known as America's Hat... CAN) where it never really warms up, then yes, this shouldn't be messed with. Your in TX, the land of year round giant bugs. Bypass it!

Change the spice, not the dish!

The only caution I have with adding flow restriction to the trans coolant line is that by slowing the flow you are creating back pressure. The fluid back pressure pushes the torque converter in to the crank harder under high load on the 4r70 series. This creates a risk of taking out your thrust bearing.

I researched the heck out of this, and am pretty sure I fell victim to it. Just a caution, that's all.

So after further researching I see my terminology was wrong. This is what I was planning for the frame. Anything against these?


Not this specific one I haven’t ordered one yet. This would be in addition to a second larger cooler up front, plus bypassing the radiator.

Is there anything wrong with eliminating the steel cooling lines and using just rubber hose? I like the idea of one solid piece of line from cooler to cooler, than cooler rubber hose splice metal splice rubber hose cooler ect...

I'm not sure that there would be much cooling actually happening with that.
I'd use a plate/Fin personally, but as others have stated they have not had any issues with a tube/fin design.
Here's something I might use. Series 8000 Plate & Fin : 13 Row Series 8000 Plate & Fin Transmission Cooler Kit

Or, go right up to the stacked plate design that is as free flowing as it gets:
Series 10000 Stack Plate : 16 Row Series 10000 Stack Plate Transmission Cooler Kit
There are different schools of thought on this though. I'm a bit more paranoid than most now and wouldn't want to add any restriction at all to the flow of fluid.

Find the thread I think Traveler made, or his idea in Turdle's truck. He used a long Super Duty trans cooler, which runs from one side to the other in front of the radiator.

The key is to not increase fluid resistance, Dono is very correct. The way to do it is to not run anything else in series. Either replace the medium sized cooler with a much larger one, or add something and split the flow properly. Run everything in parallel, that way the flow is split, the resistance is reduced or left the same.

Well glad I ask. Everyone else was saying slow the fluid down to have more time in the cooler.

So in parallel you mean two coolers with a Y, or something along those lines? Sounds complicated as I want to make as simple as possible.

So one big cooler up front and skip the radiator?

You can't run coolers spit with a Y fitting. The trans fluid will take the path of least resistance and only go through that cooler. I thought about adding one of those tube heat sink thingies you were looking at, but could not find any place. Its more for added fluid than cooling, but the more fluid the cooler it runs.

You can run any coolers in parallel. The fluid always take the easiest path(least resistance(which is very good)), but the fluid will go through both. It will achieve cooling from both. The end temperature will be less than either single cooler, which is the goal. I'd suggest "Y" fittings and not "T" fittings, that reduces restriction. Try to match coolers of similar size, not hugely different sizes if possible.

If the coolers work well enough, then you could skip the radiator cooler, but don't do that unless you are sure it isn't needed. The V6 trucks have a built in thermostat inside the trans VB, but the 302 trans(4R70W) doesn't have that. So the V6 guys can't have too large of a cooler system, but it's possible to go too big with the 4R70W(that would be a huge cooler to be too big).

Slowing the oil down too much increased the pressure on the torque converter, pushing it in to the motor. Too much pressure on the crank pushing it forward destroys the crank thrust bearing. Then your crank slops back and fourth. Very bad, ask me how I know. I have researched this at length with high performance trans guys, and the first thing they ask if you have taken out a thrust is 'Whats the oil coolant circuit line pressure?'.

I agree the oil will take the path of least resistance. If both coolers that are 'Y' d have the same fluid resistance, you are good. Is that likely? Doubt it.

You would probably be best replacing the factory one with a high end Stack plate unit that is as big as you can fit. Suddenly your mod becomes very expensive. I bet since you are in Texas, you could go with a big cooler and bypass the radiator cooler. If anything, that would probably make the oil free flow even more.
I'm not sure if that's good, or bad.
I'd like to do this, but:
1. I need to be able to heat the oil in the rad as I drive thru the winter, and it gets extremely nipply here
2. I don't want to cut the factory hard lines unless I go all in and find a shop that can convert the lines at the radiator to a AN-6 fitting for me. These would be weird fittings that I have not found yet. Also, I struggled with flaring cut lines in the past, and just don't want to risk leaks. Without an expensive tool, those lines want to crimp instead of getting a nice flare.

Doing this right will cost you, Unless you can do what CDW6212R said with the diesel cooler, but use it to replace your existing cooler. Even this will cost you in Time.

End of the day, BKennedy has had no issue with the cooler he has, and you would be fine with that also. And as CDW6212R said, using Y's with 2 high quality coolers can only help. The factory unit is actually what I would call high quality.

Yes, and just simply adding another Explorer cooler would be easy, and double cooling. I'm aiming to try one of those long SD coolers, since those will bolt right in with little trouble. I hope that size will be enough, I have two trucks needing better than stock cooling.

I already have two of the regular sized SD coolers, which are taller and would require cutting the center support. I'd rather use one that requires no cutting.

In colder climates you'd have to consider over cooling also, so the radiator cooler may have to be part of the system. I have a common remote oil thermostat device designed to function at 180*. I need to get to a machine shop to get help removing the thin cap which holds the T'stat pill inside. The device I have I was told will accept any common thermostat pill(the guts of the T'stat which moves with heat changes). I want to use a marine T'stat rated at 145*, that would keep the fluid above that temperature at all times.

The long Super duty cooler in using actually sits behind the bumper, and gets air from the vents and the gap between the bumper and body. I've got two fans pushing air through it, but I'd rather they were pulling. I'll get that worked out later. It's winter and cooling isn't a big issue now.

We need to figure out which model trucks that long cooler is in the most. I haven't been to my local JYd's in a long while, I'll try to remember to look the next time.

Start with early 2000 model F-350s with the big engines (V-10, powerstroke, etc). That's where i got my first one and the one in Jon's truck.

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Located in the manner traveler and I have done, the stock radiator fan will suck a cigarette ash thru the trans cooler at idle.

Using the pushers helps a ton. I did have 2 coolers on our black mountaineer, but to be honest you are doubling the chances of a leaking connection with 2 coolers.

I also think the single large cooler works better.