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Discussion Starter · #1 ·
I have a 2002 WRX with the 4EAT. It has a stock transmission cooler built into the radiator.Today I planned on installing my cooler to use in series with the stock on built into my radiator but Ive found conflicting arguments on whether to put it before or after the stock cooler. If I put it before the stock cooler then the thermostat on the radiator Im worried the stock cooler will just regulate it to the exact same temps its been. If I put it after the cooler than Im worried there will be no way to control the temps and it might over cool. Lots of people say you cant get the fluid too cool and others say the exact opposite. Its left me totally confused. Should I put my auxillary cooler before or after the stock cooler? Can anyone explain why I should put it before or after the stock cooler and thermostat? Thanks.
 

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What is the problem with having the system regulate temperatures exactly as it's designed to do? In other words, what are you trying to accomplish -- are you trying to ensure that the system will be able to maintain the correct temperature even under harsh conditions, or are you trying to alter the temperature of the transmission fluid? Why?
 

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^^ I'm thinking this too. Also, you Can get the fluid temp too cold. It is designed to run within a certain range. I don't know what that is, but there Is a lower end to the range. In other words, it is Not designed to run at ambient temps like on startup for long periods of time. In fact my Regal has a dealybob on it where it does not allow the torque converter to lock up until the fluid temp gets to a certain operating temp. (idea is slipping the converter heats the fluid faster) Does your car have a problem now with temps?
 

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Also, you Can get the fluid temp too cold.
^this. Having trans fluid too cold can cause just as much harm as being too hot. What exactly is the reasoning behind this mod? Are you recording trans oil temps and noticing them too high? If there is no real mechanical reason here then you might be doing more harm than good by adding another cooler.
 

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Discussion Starter · #5 ·
Hey ganm going to finally get around to installing my cooler soon so Im brushing up on my research here. First off my reason behind adding an auxillary transmission cooler is because my wrx is not stock. Sure the stock cooler works fine for a stock car but mine has a stage 2+ protune. Secondly I have seen a couple people here and there claiming that its just as bad to run your transmission fluid too cold as it is to run too hot but the majority of people have stated the opposite and say that the cooler the fluid the better. Obviously this doesnt mean 40° F or anything but how much cooler do you think a trans cooler can get the trans fluid? Also if what youre saying is true, then why do vehicles with towing packages, RVs or modified vehicles run a secondary cooler? To me that doesnt add up.

That being said Im looking for people that have done this already and can give me nsight on things like where to mount the cooler, how to route the plumbing, which cooler line on the car is the REAL inlet and outlet etc etc. Im not here to justify why I want the automatic transmission to run cooler in my moderately modified car. That information is readily available online. What I need to know, isnt. Thanks in advance everyone!
 

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Under temperature automatic transmissions are bad. Just like the engine the fluid flows at a particular rate at a particular temperature. For example my coworker had a secondary transmission cooler and a bypass for it. When he was towing he had a lot of issues with overheating the transmission would begin to slip and miss shift and eventually he had to rebuild it. After he rebuilt it he added the cooler. Because of the added cooling the transmission would always hard shift eventually killing something with the valve body. Exactly what I can't recall, but he put in a bypass system last August and hasn't had an issue sense as he can monitor the temperature and adjust cooling as needed.

I would add a temp gauge and monitor it before I add cooling to the system. If it's in a good range don't worry about it.

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The thread opens more questions that it answers. For what it's worth (which is ZERO) I'm going from memory as I don't even have an automatic transmission. If your transmission filter is a cylinder that sticks out the SIDE of the transmission, the pipe that attaches to the transmission nearest to the filter location (just above it) is the OUTLET pipe, and the pipe that goes back further, past the filter, is the INLET pipe. Except it's been many years ago, and even so then you are left wondering why the arrows on the hoses to the rad cooler seem to contradict one another... Sorry. I figure I may as well post what I remember, and ultimately it's 50-50 (not bad odds with my life...).

EDIT: Sometimes you can buy coolers at the same places that you rent trailers (for dumping dead bodies in the woods or hauling stuff etc.). The place will rent a trailer, and sell hitches, add-on lights, and transmission coolers. The ones I've looked at, for a different application, have the add-on cooler coming after the radiator in the system. They are generic instructions, but they do clearly state this.
 

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Discussion Starter · #8 ·
Thank you both for your input. It absolutely makes sense to install a temp gauge before installing the cooler. I suppose Im just growing impatient because its been sitting in the box forever and I want to hurry up and install it before I love motivation again. As for the placement, Ive really only seen 1 person give a better alternative to placing it where were talking about and He was talking about putting it inline with the trans filter(before or after i cant remember) and it was for 5eat equipped Legacys. With everyone else its either A)install it after tthe stock cooler and you can never vool your trans too much or B) cooling your trans too much is not only possible and probably, but is also just as bad as cooking it. What i dont understand is this type of thing really is a science and science is founded on facts. So with facts and physical evidence, how are there 2 polarized opinions on the matter both being stated as facts? Im wondering how many people whos transmissions were messed up from a cooler also coincide with people whos transmissions were already about to fail and they put the cooler on thinking it would help but it was already too late.
 

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I'm not a materials engineer or fluid dynamics specialist. I can only advise based off of what I have personally observed.

Like any hydraulic system in industry it operates at a particular temperature. Too hot and you roast seals, too cold and operation can be slow and create extreme pressures that blow lines. Transmission fluid is thinner so in theory I would guess it would have a wider acceptable temperature, however I don't know that for fact. It's your car and I have no skin in the game. So your choice is yours alone.

If I were to plumb in a trans cooler I would put it post filter personally, there is a lot of debris that will have the potential to move through the system and it could clog the heat exchanger.

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My 2 cents is that a stage two modified wrx/sti does not produce enough power or added force of the drivetrain to warrant an additional transmission fluid cooler. However, that is not based upon science. It is simply based upon the fact that stage 2 doesn't really push the car too much further than the stock capabilities in comparison. I would be willing to bet that your transmission fluid temperatures are withing the perfectly acceptable range. You likely wouldn't exceed this range until you started pushing way more power than the stock block could handle AND the car was used as primarily a track car.

For what it's worth, I bought a 2006 Dodge Dakota about 5 years back. This truck had an aftermarket transmission cooler. Whether or not this is because of the transmission cooler I will never know for sure, but the transmission started slipping and hardshifting at around 80k miles. I never really did any kind of towing that would warrant such mod. My guess is that the transmission constantly ran too cold. But again, this is not based on facts.

Don't take this as me telling you not to do this because it's your car and you can do what you want with it. What I am trying to get at is that you don't need to fix something until you can prove it is broken. Adding a temp gauge to try and pinpoint exactly what your trans fluid temps are would be a great place to start. Having people say that transmission fluid coolers do more harm than good in improper applications would be more than enough contradicting evidence to me to hold off a bit and investigate whether or not my car actually needs this.
 

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For what it's worth, i still havent put a trans cooler in since owning the car, over 3 motor setups and various power levels. stock to 330/380whp. And i live in NYC. Never once had the AT Temp light come on, or had noticeable reduction in performance during beatings. safe to safe my transmissions last longer than my motors.

Good fluid and fluid change intervals will keep your trans running longer than anything.
I still need to intsall my trans cooler, its only been sitting for 4 1/2 years.

And depending on where you live, you can bypass the oem radiator cooler completely. If you live where it gets cold, having the coolant help warm up the trans fluid is nice.
Most people put them after the oem cooler, no point in cooling fluid just to run it back through hot coolant again.
 
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