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Discussion Starter #1
I currently have a deep trans pan along with a Derale 13740



I have the trans cooler mounted up on my inner fender inside my engine compartment to reduce potential damage to it. To provide air flow I have swiss cheesed the fender liner below it so the puller fans can draw air up into the cooler. It has a 180 degree thermostat on it, problem that I am running into is that when towing my M1101A3 trailer, the trans is getting pretty hot, like 210-230. Sustained grades will spike it and the cooler doesn't seem to be able to keep it cooler. The temp will drop once the fans kick on but not as fast as I would like.

I do have a griffin radiator with a built in trans cooler that I have avoided using as I didn't want to heat up the radiator and correspondingly the engine with unnecessary heat.

That said, I would like to run them in tandem. Question is, should I run supply (hot) side to the trans cooler and then into the radiator or vice versa. If I run hot into the trans cooler, it will not get cooled by the Derale until the fans kick on. Usually by the time the fans kick on, the temp in the trans is already hotter. Running it through the cooler first will give the radiator an opportunity to passively cooler continuously, or would I be better off just running into the radiator and then the cooler?

Sorry for the long winding question, I doubt either way would really be that much better than the other, but while I am doing it might as well do it the best I can....
 

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Although not identical, I can provide my experience with something similar. I am running a Derale Atomic Cooler in my TJ with a 32RH automatic. My cooler was mounted on the inner fender under the hood and originally I ran just the Derale cooler, bypassing the radiator as that's what my transmission guy recommended. My transmission is a lock-up converter, but I was running a manual computer and so there was no lock-up happening.

I noticed that the temps when driving on the road for extended period would tend to get like yours in the 200ish range and even when the fan came on there was no real drp in the temperature such that the fan would turn off. This made me a little concerned, so as an experiment I plumbed it through the radiator first and then into the Derale. What I noticed was that it seemed to run a little cooler that way, although if you ran at highway speeds for a long time it would still get on the warm side, but once you slowed down it would get cool enough to turn the fan off.

So I think that the radiator may tend to act like a "damper" to the process to some extent. Off road, it never gets more than 175 or so, it was just on highway where there was an issue. Also, as a way to try and improve the air flow, I swiss-cheesed the inner fender with 1" holes so it could draw cool air in and also added louvers right above the fan (the fan is within and inch or so of the underside of the hood) so the warm air could exit easier.
 

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Run the output of the transmission cooler into the cooler integrated in your radiator...if your radiator is doing its job you should have nothing to worry about.

If that doesn't work, it is time to get a bigger transmission cooler in a spot that sees plenty of air flow.
 

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cool, so radiator first then into the cooler? Elec fans or engine on the radiator?
Trans to radiator to Derale and back to trans. Stock 4.0 engine, mechanical fan and radiator. I'm in process of stretching the front axle forward, so will likely be redesigning the whole set-up in the next few months as I'll have to go to a shorter radiator for clearance at full bump.
 

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My logic in going radiator first is that's the only cooler that a vast majority of factory automatics use and adding the Derale takes out the left overs. You could argue that the radiator actually adds heat to the fluid, but I think you are always going to have some regardless, which is why there's difference of opinion on what's best.
 

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i personally would(and im currently putting an auto in my buggy which will be the same way) run the tranny into the derale cooler FIRST then into the radiator, cooling the fluid down a little before it hits the radiator will put less strain on the radiator thats trying to cool both the engine and the tranny.
 

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i personally would(and im currently putting an auto in my buggy which will be the same way) run the tranny into the derale cooler FIRST then into the radiator, cooling the fluid down a little before it hits the radiator will put less strain on the radiator thats trying to cool both the engine and the tranny.
The problem with that is the heat exchanger in the radiator can only cool to the same temp as the coolant surrounding it. If the external cooler drops the trans fluid to say 120*, then as it passes through the radiator it could possibly be heated, instead of cooled, especially if coolant temp is 190*+.

If it goes to the radiator first, it will likely drop the fluid temps 10-50*. Remember, coolant (water) has excellent thermal properties and will absorb a fair amount of heat without much change in its own temp. Doing this will allow the trans cooler to drop the temps even further. The only limiting factor at that point would be how hot the ambient air is flowing across the external cooler. It sounds like the external fans are wired to a thermostat? Why not wire them to come on at a much lower temp, or wire them so that as long as the engine is running, they are as well. It may do a better job of keeping temps low if you stop allowing the trans to get really hot before the fans kick on
 

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Discussion Starter #11
I am thinking of adding a switch in so I can turn it on regardless of the thermostat. I also ordered all the -AN fittings and lines to run it into the radiator. The thinking above is where I was leaning as to reducing it a little bit so the derale can finish it off. Also ordered amsoil fluid and gonna see if that make any diff
 

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The problem with that is the heat exchanger in the radiator can only cool to the same temp as the coolant surrounding it. If the external cooler drops the trans fluid to say 120*, then as it passes through the radiator it could possibly be heated, instead of cooled, especially if coolant temp is 190*+.

If it goes to the radiator first, it will likely drop the fluid temps 10-50*. Remember, coolant (water) has excellent thermal properties and will absorb a fair amount of heat without much change in its own temp. Doing this will allow the trans cooler to drop the temps even further. The only limiting factor at that point would be how hot the ambient air is flowing across the external cooler. It sounds like the external fans are wired to a thermostat? Why not wire them to come on at a much lower temp, or wire them so that as long as the engine is running, they are as well. It may do a better job of keeping temps low if you stop allowing the trans to get really hot before the fans kick on
I agree with all of this. The heat exchanger can efficiently drop the trans temp close to the outlet temp of the radiator. That will make the external cooler more effective.
 

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Discussion Starter #13
just ordered up the Amsoil fluid and -AN fittings and will hopefully get to this weekend. I have sensors in the pan and the body of the trans so I can switch back and forth at the trans temp gauge so I can pretty accurately measure how effective the cooling is. Will report back when I have some test pulls under the belt.
 

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The problem with that is the heat exchanger in the radiator can only cool to the same temp as the coolant surrounding it. If the external cooler drops the trans fluid to say 120*, then as it passes through the radiator it could possibly be heated, instead of cooled, especially if coolant temp is 190*+.

If it goes to the radiator first, it will likely drop the fluid temps 10-50*. Remember, coolant (water) has excellent thermal properties and will absorb a fair amount of heat without much change in its own temp. Doing this will allow the trans cooler to drop the temps even further. The only limiting factor at that point would be how hot the ambient air is flowing across the external cooler. It sounds like the external fans are wired to a thermostat? Why not wire them to come on at a much lower temp, or wire them so that as long as the engine is running, they are as well. It may do a better job of keeping temps low if you stop allowing the trans to get really hot before the fans kick on

from all the research i have done i go by the thinking that the optimum operating temperature for the fluid in the tranny is 180-200*(some say up to 225*) so i want the radiator to warm up the fluid

if you dont have enough cooling or your racing with lots of HP i could see the need to get the temps down below the radiator temps, im just a redneck trail wheeler though.
 

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I used to run the transmission cooler lines thru the radiator and then thru my trans cooler that I had sitting in front of the radiator. My issue was that my transmission temps were not getting high enough. I daily drive my YJ and in the winter time I would be lucky to see 110. Having too cold of a transmission is almost as bad as running one too hot.

I then decided to ditch running the trans cooler lines thru the radiator and went with an inline fluid thermostat from Improved Racing. I went with the 165 degree version (they also make a 145, 185 and 215 degree units) and I've been happy with it. The transmission warms up nicely now no matter the ambient temperatures or whatever the engine temperature is running at and it works very well keeping the temps within a 5 degree window of the 165 degree rating. Just another thing to consider in case you wanted to run the two fluid systems separately. Oh and they are made in the USA with a lifetime warranty.

Linky
 

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Discussion Starter #16
I really don't have to worry about being too cool out here in Cali. I did run the lines last week and changed out the fluid to Amsoil. It ran significantly cooler this weekend on an hour long freeway trip. Used to run around 180-200 when on the freeway and now I was looking at 160 at the hottest. Gonna hook up my trailer and tow the pass behind me this week and see how that looks. So far so good, and I increased my fluid capacity too!
 

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I really don't have to worry about being too cool out here in Cali. I did run the lines last week and changed out the fluid to Amsoil. It ran significantly cooler this weekend on an hour long freeway trip. Used to run around 180-200 when on the freeway and now I was looking at 160 at the hottest. Gonna hook up my trailer and tow the pass behind me this week and see how that looks. So far so good, and I increased my fluid capacity too!
Increased capacity and a good fluid will do that for you. I've been running Amsoil in my built 4L60 and it's holding up very well. Hope the trailer test goes well for you and please keep us posted with your results.
 

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Discussion Starter #18
happy to report that the grade pull was a success. I have two trans temp sensors in the trans. One in the body in the stock location and one in the Mag Hytec pan. I have a switch next to the gauge that allows me to swap between both sensors and monitor the temp in both places. The LED under the switch lights up when the trans cooler fans kick on.

On the climb today with the trailer (about 2000 feet in 2-3 miles) the trans did warm up but nothing like it used to. Before I would be hitting 230 and this time I only hit 195 in the body and 210 in the pan.

What was interesting was the body of the trans stayed cooler than the pan. Makes sense as the return line is there, but it is the opposite of what I was experiencing.

Stoked on the outcome. Hasn't affected the heat of the LQ9 and trans is running a lot cooler. Success.

trans pan temp



engine temp at top of grade



trans body temp



old setup of the derale. Now the lines go to the radiator first.

 
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