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How to properly plumb your 5EAT transmission cooler


ClimberDHexMods

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I get a lot of questions about this, and I also spend a lot of time informing people how to fix their incorrectly-plumbed ATF cooler setups. There are a lot of well-meaning people out there with incorrect thoughts regarding cooling the 5EAT. Thus, there is a lot of less than ideal advice going around these forums and elsewhere. So this thread may serve to correct these long-standing errors. Primarily, the goal here is to get people to STOP OVER-COOLING THEIR ATF!

 

In my perfect world, ATF would always be between 160-180F. On the hot side of the range, short rises to 200F are fine and are part of normal factory-setup behavior with modern fluids prescribed to the 5EAT, especially with aftermarket synthetic ATFs. On the cold side, ATF can linger as low as 120*F pretty normally during instances when it's cold out, speeds are high, and instances of acceleration are minimal. Some say 100F is acceptable for the low side. I have not made up my mind about this. At any rate, these are good points of reference to start.

 

Please excuse the basic nature of these drawings.

 

http://legacygt.com/forums/attachment.php?attachmentid=175729&stc=1&d=1393521481

Stock. This is fine for most people. It's not perfect. ATF can be overheated, and ATF can certainly be over-cooled, in the way the car comes from the factory. This is an acceptable setup for cold climates. It is not a good setup for hot climates that have a lot of stop-and-go traffic or mountains, and is not great for towing or road course racing. If in a hot climate you do many back-to-back rounds of acceleration, or create heat some other way (towing) then you should invest in a transmission cooler, and should strongly consider a bypass thermostat as well (more on that later).

 

 

http://legacygt.com/forums/attachment.php?attachmentid=175730&stc=1&d=1393521481

This is how many people have theirs setup, and this is generally how threads tell people to setup their cooling systems. This setup can sometimes work fine, yet at other times it can be worse than stock. In cold winters, this can a step down. In the middle of summer, it can work fine. The logic somewhat makes sense if you're using incorrect assumptions. Assuming the car is a roaring fire-breathing monster, whatever temp trans fluid comes out of the radiator will be better off being cooled just a bit more, so you might as well get the biggest cooler for those potential future hill climb stages, since you never know. The reality is this takes ATF from the trans, normalizes it to the cold side of the engine coolant radiator (good, unless you're making a lot of heat during that driving session). Then through the air cooler after the radiator, the ATF is cooled down. If the cooler is big enough, this can lower temperatures close to ambient. This can potentially be bad if it's cold enough out. This works well if most of the time your transmission is producing far more heat than a normal car (it's probably not), or your engine coolant is perpetually overheated (it's probably not), or you do not drive in cold weather or on long stretches of highway. In reality, you car is producing excessive heat rarely, maybe only 1%-5% of the time, unless it's a race car that gets trailored to and from road courses. And even when excessive heat is produced, if it's only for seconds (like when drag racing or driving up one steep hill), then the stock cooling system would be more than adequately setup to handle that.

 

 

http://legacygt.com/forums/attachment.php?attachmentid=175731&stc=1&d=1393521481

This is the better way to plumb a (small) air cooler if you are certain that you want one, yet are not willing to pay the modest price and endure the moderate frustration of fitting a proper bypass thermostat. If you already have your air cooler plumbed, then this is a reasonable conversion to perform at home, though to be fair the different will be modest, not dramatic, as the radiator is not a massive liquid/liquid heat exchanger. Most important, this setup has minimal risk of allowing ATF significantly over 180F, yet will help keep ATF temp from dropping too far below 160F in the 90% of driving conditions when the ATF is easily cooled by just the radiator, and weather is warm. However, ATF temperatures can still linger around 100F with this setup in cool weather, especially in the winter, which is why a bypass thermostat is very helpful. This setup will also slightly slow down the speed at which everything initially warms up. In summary, when compared to the "poor" setup above, this version is a better version, offering more benefit with less drawback across a wide range of weather and other conditions of use.

 

http://legacygt.com/forums/attachment.php?attachmentid=175732&stc=1&d=1393521481

In my opinion, this is the only good one-size-fits-all way to plumb an air cooler: with a bypass thermostat. However, you can still have over-cooling issues with this setup (see notes below). Derale and other companies make bypass thermostats that actuate at 180F, and include 4x 3/8" barb fittings and a universal mounting bracket as either a bundle or as an add-on. Transmission rebuilds cost $$$$, ATF fluid changes cost $$$, so do yourself a favor and buy and install a bypass thermostat. It will pad out both ends of the temperature spectrum, allowing faster warmups and a more average temperature, while still offering full cooling ability when things get hot.

 

 

If you do not have an OEM Radiator (not pictured) then your best bet is to use a bypass thermostat and air cooler. This can be a bit more difficult to dial in for year-round stability if you live in a climate that has hot summers and very cold winters. You will not have the radiator to pull down hot ATF temps or pull up cold ATF temps. Over-cooling becomes very easy without a radiator, even if you have a bypass thermostat (though the bypass thermostat does help a lot). If you have a non-OEM radiator, then it's probably worth your while to buy a temperature gauge. That said, many other cars come from the factory with an air cooler and a bypass thermostat, without a radiator heat exchanger provision. The difference is those coolers are sized to provide adequate cooling from -30F to +130F while being driven normally.

 

 

 

Additional notes on cooler selection and temperature monitoring:

1) Most people on here (I have been guilty of this plenty) forget that their car will most likely spend 99% of the time NOT racing or towing heavy loads up mountains. This means that most of the time, your car is not producing tremendous amounts of heat, and thus is no trouble for just the stock radiator to regulate.

2) My opinion is that smaller transmission air coolers are satisfactory for the 5EAT, unless you're doing serious racing or serious mountain climbing, or live where it's quite hot. For example, the Long Tru-Cool 4454 is a popular model on here because it "is the biggest that will fit on one side of the center support bar." In fact, the 4451 may be plenty of cooling for you, or me, or many people, even if it appears to be quite small. Take a look at the coolers installed on big vehicles with tow packages, or small delivery trucks. Hint: These coolers work far better than you might think, depending on placement. A transmission is not an engine that produces glowing hot exhaust when you give it gas. There is no transmission combustion, no fuel being lit on fire. That said, I do not know exactly the right size for your application, more on that below.

3) These bypass thermostats only recycle around 90% of fluid at most. Even with 10% of ATF still going through the coolers, you can easily over-cool ATF in the winter. I recently talked with a 5EAT owner in Colorado who still had over-cooling (monitoring ATF temp via gauge) after installing a bypass thermostat. The solution was to temporarily (through the winter) block his big air cooler. The result was rock steady ATF temps at around 180F. When your transmission cooler is so big that it can receive just a small portion of total fluid via bypass thermostat, and it still drops aggregate ATF temperature to well below 160F, your cooler might be too big, or you might need to cover some portion or all of it until warm temperatures return. Even a covered/obscured air cooler still sheds considerable heat, even if its efficiency is reduced via deliberate obstruction.

 

I want to conclude by saying that I do not know the perfect setup for year-round stability, from cold winter to hot summer environments that will always yield a ~160-180F ATF temperature. As I said above, your best bet is probably a bypass thermostat and a reasonably-sized cooler, plumbed the right way. As for watching temperatures amid extreme heat and extreme cold, I recommend any fluid temperature gauge. Any automotive temperature gauge compatible with oil (almost all of them are), will tell you what you need to know. If you have other gauges besides a boost gauge, then you would be wise to add a temperature gauge for your 5EAT. You can tap into the fluid stream in many places, but it doesn't matter very much where as long as it's somewhere. Whether in the trans pan or T'd into the cooler line output (hot side) or return hose (cold side), you will get useful readings that will indirectly (or directly) indicate when the mean ATF temp has risen or fallen far from 180F. The reality is that some 300whp 5EAT weekend track cars on here will need greater ATF cooling provisions than most of the >400whp street monsters that will instead benefit from having a deliberately small cooler, or specifically no extra cooler at all if the circumstances are right for it. I am routinely baffled by similar people with the 4454 cooler and similar power setups reporting transmission behavior that in effect means each is seeing different ATF temperatures. Things such as typical vehicle usage, local climate, cooler placement and FMIC obstruction each make some amount of difference. When you add up everything, you end up seeing different ideal cooling setups for different cars. If you care enough to want rock solid ATF temps, then buy a gauge, and observe what happens during the hottest hot, the coldest cold, while towing up a hill, while racing, while cruising on the highway, while in stop-and-go traffic, or during whatever it is you do with your car. This will tell you what you need to know better than anyone on here can, including me.

 

Please ask any questions.

 

Thank you,

David @ HexMods LLC

1228581905_Stock5EATATFradiatorcoolingcircuit.jpg.86d8d09bbdd7b9e8a89da2c90cbf723c.jpg

1433387249_Wrong5EATATFradiatorcoolingcircuit.jpg.d6b8bc32849cde11ca88289d26f3c4b7.jpg

1195484984_Better5EATATFradiatorcoolingcircuit.jpg.f9bb82c70a97fe572980bab63c6c6bdc.jpg

1584590889_BestBypassThermostat5EATATFradiatorcoolingcircuit.thumb.jpg.6869283e01ce3e524fa98d72aace33e3.jpg

Edited by ClimberD@HexMods
[CENTER][B][I] Front Limited Slip Racing Differentials for the 5EAT now available for $1895 shipped, please inquire for details! [/I][/B][/CENTER]
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Is the 4454 too much cooler(with a bypass) in stand alone? Such as running a mushimoto rad with no trans cooling provisions.

 

 

I really need to get a gauge and see what my stock temps look like for various situations. Towing, stop and go/city, mountains, etc. Get a great base line

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Hello climber, I already have contact you for a Hexmods VB but I still making some repair on mi 2005 LGT wagon I have a bad radiator and that cost me a lot of $$$ on cylinder head gasket change, so I have a question I live on a tropical country no snow and no cold weather, I only can get aluminium radiator without the tranny cooler part, so I thinking about put only a external tranny cooler, which can be the correct way to do this?

 

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Is the 4454 too much cooler(with a bypass) in stand alone? Such as running a mushimoto rad with no trans cooling provisions.

 

It depends on what you're doing and what temps you drive in. Without the stock radiator, just get an air cooler and a bypass thermostat.

 

I really need to get a gauge and see what my stock temps look like for various situations. Towing, stop and go/city, mountains, etc. Get a great base line

 

Exactly, do it :) Automotive temp gauges are the cheapest ones, and are among the easiest to install.

 

Hello climber, I already have contact you for a Hexmods VB but I still making some repair on mi 2005 LGT wagon I have a bad radiator and that cost me a lot of $$$ on cylinder head gasket change, so I have a question I live on a tropical country no snow and no cold weather, I only can get aluminium radiator without the tranny cooler part, so I thinking about put only a external tranny cooler, which can be the correct way to do this?

 

Sent from my Nexus 5 using Tapatalk

 

Without the stock radiator, your best bet is a bypass thermostat and an air cooler. There are a couple people on here with 5EAT and aluminum radiator. I don't know what will end up being the right size air cooler for you. Are you interested in installing a temperature gauge?

[CENTER][B][I] Front Limited Slip Racing Differentials for the 5EAT now available for $1895 shipped, please inquire for details! [/I][/B][/CENTER]
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Damn. Mine is a 4EAT but looks like I will be re - plumbing my cooler.

 

I have mine set up like the first example (minus the filter). Hot days I will see 180-200 degrees on my gauge (the sensor is in the return line just outside the trans) during stop and go traffic, and 140-160 on the highway.

Wintertime....I might see 120-140 in traffic and it's pegged at 100 (low side obviously) while on the highway.

 

Thanks for the informative post

 

Btw.. wanna mod my vb as a 4EAT test run??? :)

Edited by bomberlegacy
'08 Legacy 2.5i - hybrid intake - delta 1000 - E85 - magnaflow exhaust
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I think I can monitor the tranny temp with the obd2 blue tooth adapter and a android table I use as gauge, I will check, the Trans cooler need a fan or just I can put it on the front of my radiator? Where I can find a bypass thermostat, and which one did you recommend?

 

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Thanks so much! This makes me feel much better - I've always felt a little nagging that I had never installed that Tru-Cool 4454 (IIRC) that I bought. And of course, my initial instinct was to do "poor setup #1".

 

Given that I live in NorCal (ambient temperatures for the most part are 50-80 year round), and the most spirited driving I do is the occasional on-ramp run or quick-pass after some stop-and-go traffic, I have a feeling leaving it stock is my best bet, other than a full bypass+cooler setup. Even then, it might not be that useful.

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I think I can monitor the tranny temp with the obd2 blue tooth adapter and a android table I use as gauge, I will check, the Trans cooler need a fan or just I can put it on the front of my radiator? Where I can find a bypass thermostat, and which one did you recommend?

 

Sent from my Nexus 5 using Tapatalk

 

http://img.tapatalk.com/d/14/02/28/5uhu8uhe.jpg

 

My setup

Derale bypass

Tru cool 4454

Edited by RooTBeeR

"Build" Thread <--Link

(OLD) '05 EJ255 now a '13 EJ257 Bottom End w/D25 heads (NEW)

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Damn. Mine is a 4EAT but looks like I will be re - plumbing my cooler.

 

I have mine set up like the first example (minus the filter). Hot days I will see 180-200 degrees on my gauge (the sensor is in the return line just outside the trans) during stop and go traffic, and 140-160 on the highway.

Wintertime....I might see 120-140 in traffic and it's pegged at 100 (low side obviously) while on the highway.

 

Thanks for the informative post

 

Btw.. wanna mod my vb as a 4EAT test run??? :)

 

The 100 on the highway is the problem (for most people). If you do change it up, please report back.

All set on existing 5EAT projects for now before getting into any more new stuff, thank you.

 

I think I can monitor the tranny temp with the obd2 blue tooth adapter and a android table I use as gauge, I will check, the Trans cooler need a fan or just I can put it on the front of my radiator? Where I can find a bypass thermostat, and which one did you recommend?

 

Sent from my Nexus 5 using Tapatalk

 

If bluetooth OBDII can read trans temp on a 5EAT, that would be a) new, b) awesome. Please let us know if it works!

You do not need a fan. The front of the car gets plenty of air flow to cool anything and everything.

As he said, Derale thermostat on SummitRacing and Amazon, probably easiest to get the one with the included 3/8" barbed fittings and mounting bracket.

http://derale.com/products/coolers/accessories/fluid-control-thermostats/15-heavy-duty-stainless-steel-standard-rotation-flex-fan-chrome-detail

 

Thanks so much! This makes me feel much better - I've always felt a little nagging that I had never installed that Tru-Cool 4454 (IIRC) that I bought. And of course, my initial instinct was to do "poor setup #1".

 

Given that I live in NorCal (ambient temperatures for the most part are 50-80 year round), and the most spirited driving I do is the occasional on-ramp run or quick-pass after some stop-and-go traffic, I have a feeling leaving it stock is my best bet, other than a full bypass+cooler setup. Even then, it might not be that useful.

 

Stock really isn't that bad, and all adding a cooler will do is make stock colder. So you don't really need a cooler unless you're making a lot of heat, a lot more than the radiator's integrated heat exchanger can remove.

 

http://img.tapatalk.com/d/14/02/28/5uhu8uhe.jpg

 

My setup

Derale bypass

Tru cool 4454

 

Nice. This is the same setup that I just talked about on the phone with a person in Colorado, who still had to block the whole 4454 during the coldest winter months, even with the bypass thermostat. Just a heads up for you to keep an eye on.

[CENTER][B][I] Front Limited Slip Racing Differentials for the 5EAT now available for $1895 shipped, please inquire for details! [/I][/B][/CENTER]
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I'm in southern California, so the lowest it get near me is mid 30's, at night, for about a week or two/year lol still 50-70 in the day after that haha

 

I should be could.

 

But I do drive (towing) the mountains in the teens occasionally.

And to my brothers place in Co(hour south of Denver)

 

So yeah ive had it a few months and haven't installed it because no gauge, and no base line tepms to go off of

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I'll add that the proper way to monitor the ATF temp on a 5EAT is via the internal trans temp sensors using the OBD port. That gives accurate, in-situ ATF fluid temps from the bowels of the beast. An external gauge will only be relative to the real deal in the trans, showing you that your ATF is being nicely cooled, or not, by whatever cooling setup you have. But once that fluid is back in the pan, it's coming up to cooking temps nice and quick. Sous vide, anyone? If you want an external gauge, then it should be plumbed in before the cooler, as close to the transmission as possible to more accurately monitor the actual ATF temps within the trans.

 

What's important in a cooler is that it cool an adequate amount when necessary. What's an adequate amount? As David illustrated, it depends on the car, the driver, and the conditions. I've got lots of lady friends with OBXTs that will never need more than stock cooling. Preventing long term fluid overheating is what's paramount. It really doesn't take too many incidents of overheating even quality ATF to severely degrade it. Any stock 5EAT with decent power in front of it is capable of toasting its fluid, even with as much cooling as you can throw at it. Looking at scorched blue transmission steels and clutch packs reveals that's the most dangerous heat source from the ATF's perspective: extreme pressure, sheering, and heat generating friction, with the fluid laid out nice and thin and at its most vulnerable. Built 5EATs and those with VB mods will generate less heat internally than a stock 5EAT. In fact, a VB upgrade is probably the best "cooling" solution for a 5EAT, but I don't think you can put too big a cooler in place, especially if you use a thermostat with it. My testing shows that even with a large Hayden 678 as the only cooler, temps can still linger over 200* for a prolonged period of time in summer heat after having beat on the car.

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^^^ Very well said. The 5EAT internally reads a lot higher than externally (after being pumped), maybe +10F. Makes sense, the aluminum valve body is sitting right under everything, and hot converter fluid goes back into the valve body (momentarily). ATF gets the hottest after the converter, right before entering the external cooler lines. I'm not so worried about this converter temperature spike on acceleration. Our torque converters tend to have no problems. It's the steels that worry both of us.

 

Important to note that you do not have an OEM radiator with ATF heat exchanger. You also live in New Mexico, which does get a little bit cold, but not nearly as cold as home base of half the people on here (yet still colder than anyone on the CA coastline). I know of people who basically had your setup and had to install a thermostat; too cold.

 

I edited the write-up to loosen the strictness of my first version. I'll make an effort to keep it updated, along with the other bazillion things going on. The main point is now when people PM me asking if they need a cooler, I'll just send them here :)

 

I will edit again later to reflect these considerations you point out.

Edited by ClimberD@HexMods
[CENTER][B][I] Front Limited Slip Racing Differentials for the 5EAT now available for $1895 shipped, please inquire for details! [/I][/B][/CENTER]
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Excellent information and thank you.

 

Would you recommend anything different for a 2013 3.6R?

"It's within spec" - SOA :rolleyes:

"Depth is only shallowness viewed from the side." - Fredism

"So, how much did it cost for your car to be undriveable :lol:." - Stephen (very close friend)

"You have done so much it would be stupid to go back." - Sunny of Guru Electronics

 

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Excellent information and thank you.

 

Would you recommend anything different for a 2013 3.6R?

 

I know nothing about that car specifically, as far as what all the ATF cooling needs are. If no one on this forum does either, then hookup a temp gauge and be the first! I have spent little time following the 5th Gen cars :(

[CENTER][B][I] Front Limited Slip Racing Differentials for the 5EAT now available for $1895 shipped, please inquire for details! [/I][/B][/CENTER]
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  • 4 months later...

Read this and did some logging. I was interested as I figured living in Brisbane it doesn't get that cold so my setup (ClimberD's "poor" cooling circuit) should be fine (I say doesn't get that cold as Brisbane had it's coldest night last night in 100 yrs and lowest temp was 2.7*C / 37F). Did a log run after oil and coolant temps were in normal operating ranges (centre of gauge for coolant and oil over 75C/165F) at highway cruising speed...ATF never got above 127*F :( whoops. Ambient outside temp at the time was 10*C/50F. Times for re plumbing and thermostat. Although, I dare say this setup is required in summer where is rarely drops below 30*C/85*F for about 2-3 months straight.

 

Thanks for the thread! A great read

Edited by Sean82
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I got one on my 3.6r. It is not run with a thermostat nor a valve. I am in california, so not as worried about weather.

"It's within spec" - SOA :rolleyes:

"Depth is only shallowness viewed from the side." - Fredism

"So, how much did it cost for your car to be undriveable :lol:." - Stephen (very close friend)

"You have done so much it would be stupid to go back." - Sunny of Guru Electronics

 

2018Q50RS | 2015WrxThread | Shrek

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http://legacygt.com/forums/attachment.php?attachmentid=105521&d=1316498801

 

http://www.subaruoutback.org/gallery/502/9672tranny_cooler_mounted.jpg

 

 

Check out this thread.

http://legacygt.com/forums/showthread.php/transmission-cooler-installation-17293.html?p=3809820

"Build" Thread <--Link

(OLD) '05 EJ255 now a '13 EJ257 Bottom End w/D25 heads (NEW)

Forever Slow

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  • 11 months later...
  • 1 month later...
http://img.tapatalk.com/d/14/02/28/5uhu8uhe.jpg

 

My setup

Derale bypass

Tru cool 4454

 

 

 

 

Finally finished up my trans cooler.

 

http://images.tapatalk-cdn.com/15/08/23/b865f1add788a74224ac80aec3e52e56.jpg

 

http://images.tapatalk-cdn.com/15/08/23/16cefa8efafda8b16ba309c4ed283580.jpg

 

http://images.tapatalk-cdn.com/15/08/23/3f6263fbc2029c4526c146ffea46d500.jpg

"Build" Thread <--Link

(OLD) '05 EJ255 now a '13 EJ257 Bottom End w/D25 heads (NEW)

Forever Slow

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  • 2 years later...

Installed a transmission cooler and thermostat when I replaced my radiator. Noob question - which line is the flow from the transmission and which is the flow from the radiator?

 

I have read the forum back and forth, and have looked at parts diagrams but the information is not clear - some individuals claim it is the line closest to the engine, other say it is the line closest to the radiator. I have identified which line feeds the filter, and if I understand correctly the flow goes from 5EAT->filter->radiator->5EAT.

 

Any help is appreciated.

 

PS - I mounted the thermostat behind the bumper on the drivers side, as recommended by another LGT.com member and it fit like a charm!

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