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OEM Transmission Cooler


AlabamaDan
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Hey y'all!  I was at the JY today and they had a 1997 QX4 so I looked for some parts I was in need of.  I was super excited to find it because of the easy of installing (so I thought) with brackets made to fit existing holes that are probably already in my frame.   It's in the red box in the diagram below. I was surprised to find that it still goes through the radiator then into the cooler and then back to the transmission. I've heard folks that say they had issues with the radiator clogging and causing transmission failures.  I have a brand new radiator.  Should I keep this OEM configuration or bypass the radiator?

 

It's in the red box in this diagram:

QX4%20Transmission%20Cooler_zpsckxnyplz.

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My radiator is completely bypassed. We will see how it does this winter though. I’ve read about people having issues with low trans temps (no torque converter lockup) with the radiator completely bypassed.

I have loosely put together a list of parts for a temp control system that would bypass the cooler until a specified temp is reached but it’s expensive and complicated.. the problems are the solenoid valves (12VDC options are limited and rectifying higher voltage is going to make things even more expensive, have to select high quality stuff because a failure would mean transmission failure) and open/close timing to make sure there are no interruptions in flow..

Anyway, I bypassed mine completely because I saw trans temps at 235degF and that’s just ridiculous. The integrated trans cooker is only good for warming the trans up and keeping it under 250 or so during the summer. Ridiculous.


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Ford had a thermostat bypass for the trans coolers on later Crown Vics. Sounds like it was more trouble than it was worth; marginal benefit when it works, overheated tranny when it doesn't.

 

I've got mine plumbed with an aftermarket cooler in line with the stock one, the same as your Q apparently. It's a fairly new rad so I wasn't worried about gunk, and by the time the slushbox pukes up enough material to clog a cooler, arguably the cooler's the least of the system's worries. I've never bothered to hook up a temp gauge for the transmission to see how much good this setup is or isn't doing.

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I haven’t nailed down which controller I would like to use.. this one seems great but it’s only $30 which is worrisome.

https://www.amazon.com/Lightobject-ETC-JLD612-DC-Fahrenheit-Temperature-Controller/dp/B00C9M6ZJC/ref=mp_s_a_1_31?ie=UTF8&qid=1539090194&sr=8-31&pi=AC_SX236_SY340_QL65&keywords=12v+dc+temperature+controller&dpPl=1&dpID=41bregD4ztL&ref=plSrch

You have to buy a temp probe and a barstock tee or the likes and whatever bushings you’d need to set the probe at the right depth.

At the very least you could monitor the temperature and if it the trans cooling system needs to be controlled then your already started in what you need to make it happen.


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  • 2 months later...

I too am revisiting this in my head.. I have noticed, for me with a bypassed radiator, if the conditions are right that I will dip below operating temp which kicks lockup off and subsequently raises trans temps allowing lockup again. It only happens one time when I first reach operating temps AND there is a long downhill stretch.

Not a big deal but it definitely makes me want to at the very least be able to monitor temps..

I am interested to know what TowndawgR50 experiences up where he is.

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Bypassing the cooler based on need is going to be expensive and there doesn't appear to be a way around it.. unless you want to plumb a hand operated directional ball valve somewhere that's accessible while driving... hmmmmm.. you really could do such a thing. You could have one of the outputs on the controller turn a lamp on to let you know its time to switch the valve to run thru the cooler and a second alarm with something audible and maybe a red lamp or something when the temps are higher than desired. You could even run with the valve in between positions and change it based on need...

 

interesting

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13 minutes ago, onespiritbrain said:

Bypassing the cooler based on need is going to be expensive and there doesn't appear to be a way around it.. unless you want to plumb a hand operated directional ball valve somewhere that's accessible while driving... hmmmmm.. you really could do such a thing. You could have one of the outputs on the controller turn a lamp on to let you know its time to switch the valve to run thru the cooler and a second alarm with something audible and maybe a red lamp or something when the temps are higher than desired. You could even run with the valve in between positions and change it based on need...

 

interesting

 

I don't understand one thing you wrote.

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If you bypass the radiator and use only the cooler then you can have trouble with trans temps being too low during very cold ambient temps since your not getting the heat from combustion at the radiator. The radiator kind of acts like a heater during the winter. If the temp is below 125degF (I think) then the torque converter will not lock. At best you will have lower gas mileage and at worst the oil is going to degrade from shear forces inside the torque converter leading to premature wear since the normal oil life cycle will not be as long.

 

The solution is to create a system that will divert the oil from going thru the cooler when the temps are below 125degF. That requires a controller to look at the oil temp and actuate a valve (or valves), bypassing the cooler and routing the oil straight back into the trans.

 

The parts need to be reasonably high quality since failure will kill the transmission and quality is expensive. Especially when you are looking at parts that are generally used in industry and the usual customer is a company instead of an individual.

 

I can’t find a directional solenoid valve under $150 and those are only 1/4” valves.. Temp controllers are usually quite expensive as well but I have found a few that are cheap.

 

Anyway I haven’t had too much trouble with temps being too low here in Georgia but the dead of winter isn’t here yet. People that live way up north where ambient temps can be sub zero might never see 125degF trans temps.

 

I’m thinking a high quality oil cooler bypass system is going to be a little north of $500 just to gather parts.

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I have the factory cooler on my 03 completely bypassed and haven’t had any problems in winter. Granted, Delaware isn’t what I would consider super cold, but I routinely drive it in sub freezing temps (20 degrees or so). I don’t have a trans temp gauge so I have no idea what the temps run but it shifts snoothly abd has never behaved any different than when it was still running the factory set up. I went with the external cooler for mine because I use it for towing and wanted to be sure the temps stayed down under those conditions. 

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The vast majority of OEM trans oil coolers are inside the bottom or sides of the radiator. Sometimes there is an additional cooler for extra cooling capacity when the integrated radiator based cooler isn’t enough. Actually a bunch of Pathfinders/QX4s have an additional cooler from the factory.

 

I don’t trust engine coolant and transmission oil so close together... especially since Nissan has major problems with R51 Pathfinder’s trans oil coolers leaking coolant into the trans oil and oil into the radiator!

 

I believe bypassing the integrated radiator trans oil cooler is a good mod in ANY vehicle. Normal trans temps are usually 125degF to 185degF and your engine coolant temps usually hover at 185degF at the coolest. If the integrated cooler was 100% efficient then you’d still have trans temps higher than desired..

 

I measured temps over 235degF with the integrated cooler. I can’t remember now whether it was before or after I found my radiator to be stopped up, but trans oil temps over 235degF is not good. There is a section of uphill freeway that always kicks me out of lockup and I guarantee trans temps were even higher after it!

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I run my cooler independent of the radiator. I tow an 18ft toy hauler and when its loaded the weight hovers around the R50 max recommend capacity of 5k lbs so I wanted dedicated HD cooling. I don't currently have a temp gauge but I definitely want one. I monitor everything through my OBD2 real-time when towing but it doesn't have any trans readouts. 

 

The only downside of bypassing the radiator for me has been that when temps are low,  less than 32°F, for first few miles of driving after a cold start the transmission wont shift into OD while it gets up to operating temps. This has barely been noticeable since I cant reach any significant speed (legally) on the country roads around my house before getting on a highway. Other than the cold start scenario there have been no adverse effects of this setup. 

 

 As for the temperature controlled valve system- I personally would not ever trust a system like that because if it fails and I'm towing or miles away from any civilization and services on a 4X4 trail the transmission failing could potentially put my family and I in serious trouble. 

 

 Now, on the other hand, a manually actuated valve @onespiritbrain mentioned is appealing and pretty easy to do. Same design and functionality of older vehicles with a manual choke. 

Edited by TowndawgR50
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Inspired by @onespiritbrain I looked into a straight forward solution to cold weather starts while using an external cooler and adding a temp gauge. Nothing fancy but I feel like I may end up using something like this. The valve would be manually actuated from inside the cab and the gauge could be mounted in a variety of places.

Would require:

-Temp gauge kit

-simple 3 port manifold

-3 way diversion valve

-brass T fitting

-hose and clamps

nQptZeO.jpg

Edited by TowndawgR50
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21 hours ago, Bax03SE said:

Delaware isn’t what I would consider super cold, but I routinely drive it in sub freezing temps (20 degrees or so).

 

I think cold is a relative term!  It's 46*F here right now and we consider that FREEZING!  :lol:

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Fantastic diagram TowndawgR50!  I think given the temp ranges down here this isn't a big concern for me.  Besides, if I had a gauge I could tell that the tranny fluid was too cool as well as too hot, right?

 

I spoke to a local transmission shop, say a place like Mr. Transmission, about this scenario on this specific vehicle.    They were careful not to say anything that would put them liable for anything, but implied that they would not use the radiator due to issues it had.

 

 

Edited by AlabamaDan
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