Project Unicorn - a light duty trail rig

[burntkat]

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.

 

[cal]

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

 

[burntkat]

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.

 

[cal]

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?

 

[Green XJ Jeep]

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.

 

[Tbone289]

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.

 

[cal]

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.

 

[Tbone289]

From the Hayden installation sheet:

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.

 

[StinkyFab]

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?

 

[Tbone289]

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...

 

[cal]

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.

 

[Tbone289]

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.

 

[Tbone289]

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.

 

[Tbone289]

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:

 

[burntkat]

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.

 

[cal]

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.

 

[sidewaysstarion]

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.

 

[Tbone289]

Leave him alone. We're just boring him.

 

[Vintage Smoke]

So......
Toilet paper over the top of the roll or underneath?

 

[rockclimber]

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