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  #136  
Old September 6th, 2017, 07:23
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
Not sure if I want to run it back through the radiator cooler on the way back to the trans or not - strong arguments to be made both ways.
There are no good arguments to be made for running it back through the radiator cooler after going through an external one, unless one lives in the Arctic.

If you aren't seeing sub-zero temps regularly, you can't overcool your transmission. Period, full stop.
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  #137  
Old September 6th, 2017, 07:32
Green XJ Jeep Green XJ Jeep is offline
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Re: Project Unicorn - a light duty trail rig

Quote:
Originally Posted by burntkat View Post
There are no good arguments to be made for running it back through the radiator cooler after going through an external one, unless one lives in the Arctic.

If you aren't seeing sub-zero temps regularly, you can't overcool your transmission. Period, full stop.
The primary use of the "cooler" on the radiator is to aid in warming up the trans fluid quicker, not cooling.
As far as i know common practice is to run it through the rad first to aid in warm up then to cooler.
Yes it is entirely possible to over cool your trans fluid.
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  #138  
Old September 6th, 2017, 08:26
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cal cal is offline
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Re: Project Unicorn - a light duty trail rig

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Originally Posted by burntkat View Post
There are no good arguments to be made for running it back through the radiator cooler after going through an external one, unless one lives in the Arctic.

If you aren't seeing sub-zero temps regularly, you can't overcool your transmission. Period, full stop.

Keeping the fluid at operating temp.

Keeping it at *more consistent* temp.

It would also actually make installation easier too, not that I'm worried about that.
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  #139  
Old September 6th, 2017, 08:30
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Re: Project Unicorn - a light duty trail rig

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Originally Posted by Green XJ Jeep View Post
As far as i know common practice is to run it through the rad first to aid in warm up then to cooler.
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.
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  #140  
Old September 6th, 2017, 08:39
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Re: Project Unicorn - a light duty trail rig

Stopped by the shop on my way home last night and slammed a power steering cooler in.

Nothing super special here. There's plenty of slack in hoses to get around the radiator, once I install it.



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  #141  
Old September 6th, 2017, 09:41
burntkat burntkat is offline
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Re: Project Unicorn - a light duty trail rig

Quote:
Originally Posted by Green XJ Jeep View Post
The primary use of the "cooler" on the radiator is to aid in warming up the trans fluid quicker, not cooling.
As far as i know common practice is to run it through the rad first to aid in warm up then to cooler.
Yes it is entirely possible to over cool your trans fluid.
I completely disagree, from an engineering standpoint.

The cooler in the radiator is a cooler. I wonder if that's why they call it that.

The transmission makes PLENTY of heat on its own, with the torque converter slipping.

You really ought to learn what you're talking about before going spouting nonsense on the internet.
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-89 S-10: SAS, D44s front/rear. 5.7L V8. 700R4 with 4L60E upgrades. Built in my driveway.
-90 XJ 4.0, AW4, 231J: Clayton's longarms, RE 5.5" coils, hybrid 6" leaf pack, 33/12.50/15" MTs, Rancho 99012s and 99624s, Tera HD SYE, custom sliders, BW flares. Rehabbing with D44s, RE spring packs, RE 4.5" coils, and ACOS.
-94 ZJ: Budget boost, 31s. The wife's DD.
-97 XJ: Son's DD. 4" lift, ACOS, 4" spring pack, Upcountry coils, 31s
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  #142  
Old September 6th, 2017, 09:42
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Re: Project Unicorn - a light duty trail rig

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Originally Posted by burntkat View Post
I completely disagree, from an engineering standpoint.

The cooler in the radiator is a cooler. I wonder if that's why they call it that.

The transmission makes PLENTY of heat on its own, with the torque converter slipping.

You really ought to learn what you're talking about before going spouting nonsense on the internet.
According to both the performance transmission guy i use and the jeep dealership.. he is right and you are wrong.

/me shrugs
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  #143  
Old September 6th, 2017, 09:42
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
According to both the performance transmission guy i use and the jeep dealership.. he is right and you are wrong.

/me shrugs
You need to find different people to listen to, then.
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-89 S-10: SAS, D44s front/rear. 5.7L V8. 700R4 with 4L60E upgrades. Built in my driveway.
-90 XJ 4.0, AW4, 231J: Clayton's longarms, RE 5.5" coils, hybrid 6" leaf pack, 33/12.50/15" MTs, Rancho 99012s and 99624s, Tera HD SYE, custom sliders, BW flares. Rehabbing with D44s, RE spring packs, RE 4.5" coils, and ACOS.
-94 ZJ: Budget boost, 31s. The wife's DD.
-97 XJ: Son's DD. 4" lift, ACOS, 4" spring pack, Upcountry coils, 31s
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  #144  
Old September 6th, 2017, 09:58
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Re: Project Unicorn - a light duty trail rig

That's one possibility yes.

If the dealership and the trans guy disagreed, I'd be dismissing what the dealer said. Conventional wisdom says bypass the trans.

But, we've got a JK with a lifetime warranty. Dealer installed an aftermarket trans cooler, and ran it back through the radiator on the return. Included paperwork that if we bypass the radiator cooler, voids the warranty on the transmission. That's a big statement.

The guy building the race trans's for the KOH car is in full agreement with the dealer that the return needs to go through the radiator - heavily fluctuating temps will be a bigger problem than the hair extra heat you may or may not have in total.


And then we have a guy on the internet who says otherwise?
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  #145  
Old September 6th, 2017, 11:15
Green XJ Jeep Green XJ Jeep is offline
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Re: Project Unicorn - a light duty trail rig

Quote:
Originally Posted by burntkat View Post
I completely disagree, from an engineering standpoint.

The cooler in the radiator is a cooler. I wonder if that's why they call it that.

The transmission makes PLENTY of heat on its own, with the torque converter slipping.

You really ought to learn what you're talking about before going spouting nonsense on the internet.
And you should do a little research on your own before you start to insult folks.
I stand corrected on the routing but unlike you i do know what the parts of a radiator actually do and why they are there
The trans will genrate enough heat on its own which is why i said "warm up". Optimal operating temp for trans fluid is around 170ish degrees. It was designed for maximum lubrication and wear protection at that temp.
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  #146  
Old September 6th, 2017, 11:32
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Tbone289 Tbone289 is offline
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Re: Project Unicorn - a light duty trail rig

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Its actually the other way around. Trans -> cooler -> radiator -> trans.
Not according to the installation instructions for every aftermarket cooler I've seen, B&M and Hayden being good examples. Both of them recommend putting the aux cooler after the radiator heat exchanger for most efficient cooling. The transmission builders I've spoken to agree with that setup as well.

I figure the cooler manufacturers have tested more cooling setups than I have, so I follow their recommendations.

Last edited by Tbone289; September 6th, 2017 at 11:37.
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  #147  
Old September 6th, 2017, 11:37
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Re: Project Unicorn - a light duty trail rig

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.
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  #148  
Old September 6th, 2017, 11:44
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Tbone289 Tbone289 is offline
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Re: Project Unicorn - a light duty trail rig

From the Hayden installation sheet:

Quote:
In-Series: The recommended cooler connection is the "in-series" installation...This method provides maximum cooling by returning the coolest oil directly to the transmission


They even recommend a 2X bigger cooler if you're going to bypass the stock one.

Last edited by Tbone289; September 6th, 2017 at 11:50.
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  #149  
Old September 6th, 2017, 11:52
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StinkyFab StinkyFab is offline
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Re: Project Unicorn - a light duty trail rig

Cooler manufacturers don't have to replace transmissions under warranty, vehicle manufacturers do. Who do you think has a bigger stake in keeping the trans alive?
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  #150  
Old September 6th, 2017, 12:00
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Tbone289 Tbone289 is offline
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Re: Project Unicorn - a light duty trail rig

They also have a bigger stake in other things as well, such as the cheapest method of manufacturing for the best profits. I can't determine exactly what stakes were involved in Jeep's final decision, can you? Do you really feel that one route would have an impact on longevity vs. another? If longevity were such a big consideration, don't you think they would have put the aux cooler on every XJ they sold, regardless of how it's plumbed?

I've seen many other vehicle models plumbed this way (trans>rad>aux>trans). What is it with their systems (and the ones the cooler manufacturers have tested) that makes them so different from the XJ?

It makes sense to me that you would want the most efficient cooler last in the chain, before the fluid is returned to the trans. From what I've seen of my own fluid temperatures, the air/oil exchangers are generally more efficient than the stock water/oil exchanger, especially as operating temperatures rise.

If it makes you feel better to do it the other way around it's no big deal, because I don't think it's really going to make a huge difference...

Last edited by Tbone289; September 6th, 2017 at 12:10.
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