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  #151  
Old September 6th, 2017, 12:08
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Re: Project Unicorn - a light duty trail rig

That isn't what the documentation I have says. But its also irrelevant. Hayden and B&M aren't the sources I trust.

This is a little confusing because diagrams don't scan well, but here is the best diagram I can find of the factory radiator only cooling. Note the fluid enters the radiator at the bottom and exits at the top, which I can confirm is what my jeep does, and every vertical flow cooler should do. This image is from Dorman, but is the clearest diagram I could find.



Here is from the FSM diagramming routing with the factory auxillary cooler option. Notice it runs from the auxiliary cooler to the bottom of the radiator. This jives with what the dealer mechanics claim is the correct way as well as what the transmission shop shop suggests. Don't even try to tell me they decided to route through the transmission backwards, nobody here is that dumb.



Going to the radiator first would probably remove more heat yes, but it would do it by pumping that heat into the engine coolant. Why would I want to do that? I don't. The dealer doesn't want me to. The trans guy doesn't want me to.

I'll either go trans -> cooler -> radiator -> trans, or just trans -> cooler -> trans.

I feel like this entire conversation is a lot of reinventing the wheel. Particularly in light of the fact that I've done this about 15 times before, and killed several transmissions before learning what actually works vs what people spew out claiming they expertly know.

The real point of the post, and still somewhat undecided on my part - is do I install the cooler in front of the mechanical fan or aux electric fan.


Its going to be the aux fan, and I'll have the ECU reprogrammed to lower the fan temp down to what I want it to be.
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  #152  
Old September 6th, 2017, 12:20
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Tbone289 Tbone289 is offline
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Re: Project Unicorn - a light duty trail rig

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Originally Posted by cal View Post
Going to the radiator first would probably remove more heat yes, but it would do it by pumping that heat into the engine coolant. Why would I want to do that? I don't. The dealer doesn't want me to. The trans guy doesn't want me to.
You're already pumping heat into the coolant without the aux cooler, and you would be pumping less into the radiator with an aux cooler regardless of where it's located, since the overall heat of the fluid is lower.

So, taking into account what you've said, If your objective is to cool your transmission most efficiently put the aux cooler after the radiator. If your objective is to cool your transmission more, but also remove some load from your cooling system (water), then put the aux before the radiator.

I can agree with that, but my priority when installing a transmission cooler is to cool the transmission the best I can. I think if I were really concerned with the load on the radiator, I would bypass it completely and use a large cooler. I use a small cooler so it doesn't block as much cool air to my radiator.

Last edited by Tbone289; September 6th, 2017 at 12:25.
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  #153  
Old September 6th, 2017, 12:23
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Re: Project Unicorn - a light duty trail rig

I put the cooler in front of the mechanical fan so that it's always working, even when the vehicle is moving slow or is stationary. My aux fan very rarely kicks on, so most of the time the aux cooler would be doing next to nothing at very low to zero speeds if it were in front of it.

Last edited by Tbone289; September 6th, 2017 at 12:51.
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  #154  
Old September 6th, 2017, 12:46
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Re: Project Unicorn - a light duty trail rig

I think you might want to take a look at your diagrams a little closer. If the aux cooler is before the radiator, why does it clearly show that the cooler return line is coming from the top of the aux cooler, and not from the radiator?



You should read this as well, highlighted in blue, from the 2000 XJ FSM:


Last edited by Tbone289; September 6th, 2017 at 13:17.
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  #155  
Old September 6th, 2017, 14:58
burntkat burntkat is offline
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Re: Project Unicorn - a light duty trail rig

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Originally Posted by cal View Post
I just looked them up, Hayden says to bypass the radiator, B&M does in fact say to do as you do.

Chrysler/Jeep still says otherwise though, and I feel like I should trust them over B&M.
The transmission coolers don't want to sell you another car.
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  #156  
Old September 6th, 2017, 15:59
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Re: Project Unicorn - a light duty trail rig

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The transmission coolers don't want to sell you another car.
Maybe you missed the part about having a lifetime warranty on the JK.

They aren't going to sell us another car. They aren't going to sell us another transmission. They may install 2 or 3 or 9, but it will all be on them.



Anyway, I'm bored with this subject. I can tell you the one thing I am not going to do is trans -> radiator, no matter what I end up doing. I won't argue that is the best way to get heat out of the radiator, but I do not feel it is the best way to get heat out of the car, and that's my end goal.
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  #157  
Old September 6th, 2017, 16:12
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Re: Project Unicorn - a light duty trail rig

I'm fairly sure that the reason manufacturers don't want you to bypass the radiator heat exchanger is because in cold weather, high rpm loads and high fluid viscosity can cause issues with the torque converter and possibly break the pump gears in the transmission. But being as we are in sunny CA I don't think that's much of an issue. I bypassed my stock rad and running on the highway the trans is around 150* and on the streets it gets up to 180* and a bit over 210* when pulling long grades flat out.
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  #158  
Old September 6th, 2017, 16:17
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Re: Project Unicorn - a light duty trail rig

Leave him alone. We're just boring him.
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  #159  
Old September 6th, 2017, 18:32
Vintage Smoke Vintage Smoke is offline
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Re: Project Unicorn - a light duty trail rig

So......
Toilet paper over the top of the roll or underneath?
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  #160  
Old September 6th, 2017, 20:03
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Re: Project Unicorn - a light duty trail rig

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Originally Posted by cal View Post
Its actually the other way around. Trans -> cooler -> radiator -> trans.

Which is how the OEM trans cooler, if you have the tow package, is plumbed.

Probably how I'll plumb too.
That is not how my 99 with factory tow package was plumbed

Cooler after rad. It was also mounted mostly in front of the Mech Fan.

when I put the larger F250 cooler on, I simply lengthened the hoses to get to the larger cooler.



but carry on doing things the wrong way
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  #161  
Old September 6th, 2017, 20:45
kjc1972 kjc1972 is offline
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Re: Project Unicorn - a light duty trail rig

Ok i have to chime in here. Both putting the cooler before and after the radiator can be correct for a given situation. The only way to determine where to put it is to use a trans temp sensor on the output side of the transmission to monitor the temp of the trans.The average for the aw4 should be between 150- 170. This is the optimum temp (according to the fsm i may be off a little). Does it always run at those temps no. Depending on vehc configuration, drivetrain load and the way you drive it can be higher (i've never seen it lower). The transmission needs to run at temp of 170 or so for many reasons the two main ones are that is the temp the fluid was formulated to operate at the other is that if the fluid is too cold below 150 it is not hot enough to burn out the moisture in the transmission that accumulates when the vehc is cooling down. If you run the cooler after the radiator depending on the size of the cooler the temps can actually get to cold and drop below 150. Of course this depends on ambient air temp. If you live in an area where the year round temp is warm this is not usually a problem. If you live somewhere that's warm in the summer but cold in the winter the chance of overcooling the transmission is possible in the colder months. Running the cooler before the radiator is the safest bet. Which is why most but not all manufactures run it that way. In this configuration any overcooling done by the external cooler can be countered by the hotter coolant in the radiator as it passes through the heat exchanger in the radiator. Bottom line always test get a transmission temp sensor look at the gauge you may not need a cooler (but you probably will) decide what configuration is best for you and the climate you live in and run it.
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  #162  
Old September 7th, 2017, 07:42
burntkat burntkat is offline
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Re: Project Unicorn - a light duty trail rig

Quote:
Originally Posted by cal View Post
Maybe you missed the part about having a lifetime warranty on the JK.

They aren't going to sell us another car. They aren't going to sell us another transmission. They may install 2 or 3 or 9, but it will all be on them.



Anyway, I'm bored with this subject. I can tell you the one thing I am not going to do is trans -> radiator, no matter what I end up doing. I won't argue that is the best way to get heat out of the radiator, but I do not feel it is the best way to get heat out of the car, and that's my end goal.
Yes, because no manufacturer ever screwed a customer out of a warranty claim.

If you think for a second you actually have a lifetime warranty and if anything ever breaks it will be replaced, I have some land to sell you.
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  #163  
Old September 7th, 2017, 13:06
Green XJ Jeep Green XJ Jeep is offline
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Re: Project Unicorn - a light duty trail rig

Quote:
Originally Posted by cal View Post
I can tell you the one thing I am not going to do is trans -> radiator, no matter what I end up doing. I won't argue that is the best way to get heat out of the radiator, but I do not feel it is the best way to get heat out of the car, and that's my end goal.
The best way to accomplish this then is to get a high quality trans cooler with bypass. They let fluid bypass the cooler until it gets to a pre determined (usually 170-180) temp then opens up to use the cooler.
Then you can skip plumbing into the heat exchanger in the rad all together
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  #164  
Old September 7th, 2017, 13:07
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Re: Project Unicorn - a light duty trail rig

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Originally Posted by Green XJ Jeep View Post
The best way to accomplish thos then is to get a high quality trans cooler with bypass. They let fluid bypass the cooler until it gets to a pre determined (usually 170-180) temp then opens up to use the cooler
That sounds like a potential failure point?
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  #165  
Old September 7th, 2017, 13:11
Green XJ Jeep Green XJ Jeep is offline
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Re: Project Unicorn - a light duty trail rig

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Originally Posted by JohnX View Post
That sounds like a potential failure point?
I personally have never heard of one failing but anything is possible.
I beleive they are designed to fail in open position but i am only familiar with B&M units.
They alos make external bypass valves that accomplish the same thing.
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