Lower Your Trans Temps! Mishimoto R&D: 2018+ Wrangler JL Transmission Cooler

[Mishimoto]

Hey everybody,

Mishimoto is excited to share the development behind our upcoming 2018+ Wrangler JL transmission cooler for the 2.0T, 3.6L, and 3.0L Diesel!

Take a look at the first post below and let us know what you think! We're curious to hear what kind of trans temps you guys have seen with your JL as well.

Thanks,
-Steve

Steal the Limelight – Transmission Cooler R&D, Part 1: Stock Review
​

Engines get a lot of press these days. Every manufacturer wants to flaunt their latest, most fuel-efficient, technologically advanced, or powerful engine yet. The hype is even more prominent when manufacturers make drastic changes to a long-standing model, like the 2018+ Jeep Wrangler.

When FCA announced the 2018+ Wrangler JL in late 2017, all the journalists were clamoring for headlines on the new 2.0L, turbocharged, mild-hybrid engine. How would the mild hybrid perform offroad? Would the turbo lag make it a dog in stop and go traffic? What about that 24-volt power system? Everybody forgot about the 3.6L Pentastar that’s powered the Wrangler, and over 20 other models, for almost a decade. But the 3.6L Pentastar wasn’t the only thing forgotten in the fanfare over the new 2.0T.

No matter the vehicle, transmissions never manage to garner the same amount of limelight that engines and other high-profile components do. Nobody wants to think about what happens after all the explosions and fun noises. Nobody except for us and, hopefully, you. ...Continue Reading >>>

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[Lapis]

I've been rather impressed by the stock cooling in my JLUR (2.0T w/ eTorque). Trans typically stays between 200-205. I have seen it climb up to around 225 sometimes, but still not worrying. I live in the SoCal Desert, I've been offroading in 100+ and plenty of stop-go, town driving. Last week we got to 121, still cooled well.

I intend to purchase the gladiator grill inserts for less restriction, and excited to see what you can do aftermarket.

 

[AnnDee4444]

Hey everybody,

Mishimoto is excited to share the development behind our upcoming 2018+ Wrangler JL transmission cooler for the 2.0T, 3.6L, and 3.0L Diesel!

Take a look at the first post below and let us know what you think! We're curious to hear what kind of trans temps you guys have seen with your JL as well.

Thanks,
-Steve

Steal the Limelight – Transmission Cooler R&D, Part 1: Stock Review
​

Engines get a lot of press these days. Every manufacturer wants to flaunt their latest, most fuel-efficient, technologically advanced, or powerful engine yet. The hype is even more prominent when manufacturers make drastic changes to a long-standing model, like the 2018+ Jeep Wrangler.

When FCA announced the 2018+ Wrangler JL in late 2017, all the journalists were clamoring for headlines on the new 2.0L, turbocharged, mild-hybrid engine. How would the mild hybrid perform offroad? Would the turbo lag make it a dog in stop and go traffic? What about that 24-volt power system? Everybody forgot about the 3.6L Pentastar that’s powered the Wrangler, and over 20 other models, for almost a decade. But the 3.6L Pentastar wasn’t the only thing forgotten in the fanfare over the new 2.0T.

No matter the vehicle, transmissions never manage to garner the same amount of limelight that engines and other high-profile components do. Nobody wants to think about what happens after all the explosions and fun noises. Nobody except for us and, hopefully, you. ...Continue Reading >>>

What are your thoughts on the JT grill inserts and the MaxTow 800W (or was it 850w?) radiator fan? Would these be worth while modifications with your upgraded transmission cooler?

 

[oceanblue2019]

Hi Steve - nice to see you back!

When you reference secondary radiator is this the heat exchanger for the liquid to air charge cooler?

Any chance you can get some shots of the different radiators and coolers for size reference?

We also have a power steering cooler; which is basically a single hard line across the bottom of the radiator stack. Not much cooling capacity but an effort made to run it across the airflow to get some cooling.

Also still would love to see a better heat exchanger for the liquid to air..... charge temps are our limiting factory. Along with a nice reservoir to get fluid capacity up.

 

[Mishimoto]

Hi Steve - nice to see you back!

When you reference secondary radiator is this the heat exchanger for the liquid to air charge cooler?

Any chance you can get some shots of the different radiators and coolers for size reference?

We also have a power steering cooler; which is basically a single hard line across the bottom of the radiator stack. Not much cooling capacity but an effort made to run it across the airflow to get some cooling.

Also still would love to see a better heat exchanger for the liquid to air..... charge temps are our limiting factory. Along with a nice reservoir to get fluid capacity up.

Hey John,

Yes, the secondary radiator is the heat exchanger for the charge cooler - I have some photos of it that I can post a little later along with photos of the battery cooler and primary rad. We did look at making a better heat exchanger for the charge air cooler, but with the very limited space and how densely-packed the fins are on the OE cooler, we're not sure we can do better than FCA did. I'll definitely let the team know and maybe we can revisit it or look at alternatives like a auxiliary cooler or something.

In the meantime, we have another update for the transmission cooler that shows how we were able to make some improvements over the stock design. Check it out below and let me know what you think!

Thanks,
-Steve

Steal the Limelight – Transmission Cooler R&D, Part 2: Design
​

Despite its simple appearance, improving upon the stock 2018+ Jeep Wrangler JL transmission cooler will take some clever engineering. In many cases, the solution to extracting more efficiency from a heat exchanger is to make it bigger, but with the cramped cooling stack of the JL, the size of our cooler would be limited.

In our last post, we looked at the stock 2018+ Jeep Wrangler JL transmission cooler and its home in the 2.0L Wrangler. Our performance trans cooler will fit all of the available engines and the 2020+ Gladiator, but the complexity of the 2.0T’s cooling stack makes it the perfect R&D vehicle. That complexity also restricts how much we can change the dimensions of the transmission cooler.

...Continue Reading >>>

 

[2Wheel-Lee]

I don't remember the details, but from what I recall, ZF transmissions are very peculiar about fluid replacement. I believe this requires use of the StarScan tool. I would definitely look into this before I'd consider draining the fluid to replace/upgrade the trans fluid cooler.

 

[Gorilla57]

I don't remember the details, but from what I recall, ZF transmissions are very peculiar about fluid replacement. I believe this requires use of the StarScan tool. I would definitely look into this before I'd consider draining the fluid to replace/upgrade the trans fluid cooler.

The transmissions can take "days" to get the fluid level correct. The temps have to be within a very specific range and the vid I watched said it was a big hassle even with the computer hooked up to it. Plus, from what I've been able to read, our automatics run hotter than what we think they should because of the thermal bypass valve. So, running a larger cooler may not produce much of an improvement.

 

[2Wheel-Lee]

The transmissions can take "days" to get the fluid level correct. The temps have to be within a very specific range and the vid I watched said it was a big hassle even with the computer hooked up to it. Plus, from what I've been able to read, our automatics run hotter than what we think they should because of the thermal bypass valve. So, running a larger cooler may not produce much of an improvement.

That was my recollection. I think this may be another product looking for a problem (and creating more problems along the way).

 

[Mishimoto]

Hey everybody,

Refilling the transmission fluid on these is not too dissimilar to any other automatic transmission. Here's the procedure from the service manual:

1. Raise and level the vehicle (if needed, to access the trans fill port)
2. Start the vehicle and disable ESC (hold traction control button for 6 seconds)
3. Fill the trans from the fill port in the transmission until fluid starts dripping from the port
4. Close the fill port
5. With your foot on the brake, put the vehicle into reverse and hold for 5 seconds
6. With the brake still depressed, put the vehicle in drive and hold for 5 seconds
7. Release the brake and accelerate into second gear, maintain second gear for 5 seconds.
8. Hold the brake, place the vehicle in neutral and hold 2000 RPM for 5 seconds
9. Place the vehicle in park and gain access to the transmission fill plug
10. Remove the fill plug - fluid should be just at the level of the plug. If fluid is high, allow to drain until it stops. If fluid is low, fill until fluid reaches the level of the plug.
11. Reinstall and torque the fill plug to 26 ft. lbs.

In this procedure, the scan tool is only used to check that the fluid is below 86*F before step 3 and between 86*F and 122*F at step 10.

We're not sure why this would take days to reach proper level or couldn't be done without the scan tool. We typically just use a clean catch pan and refill the trans with whatever comes out, plus the extra capacity of our cooler (in this case it will be 1/4 of a quart more). Also, since you're not fully draining the system, you could likely get away with running the trans up to 86*F, checking the level, and topping off as needed. We've had our cooler off and back on, and refilled the trans several times without issue.

We have heard that these transmissions have a thermal bypass valve that opens around 190*F, but have not been able to verify it from any of our sources or materials. If there is one, the goal of this transmission cooler would remain the same: keep the fluid as close to optimal temperature as possible. Despite what some think, it is possible to over cool transmission fluid (which is why FCA installed a fluid heater and possibly a thermal bypass valve), that's why our goal for any trans cooler is not to keep the fluid below a certain temp, but to keep it close to optimal temperatures. For the JL, it seems FCA or ZF has determined that temp to be somewhere around 190*F, so we'll try to keep fluid as close to that temp as possible.

Thanks!
-Steve

 

[Mishimoto]

Hey everybody,

Good news! The discounted pre-sale for this transmission cooler is now live on our website, check it out here!

We also have the last update in the R&D process below, including the results from our performance testing. Give it a read and let us know what you think!

Thanks,
-Steve

Steal the Limelight – Transmission Cooler R&D, Part 3: Testing
​

When we last saw our 2018+ Jeep Wrangler JL performance transmission cooler, it was nothing more than a box, constructed from aluminum u-channel, with plastic end tanks glued to it. This time, however, we’ll be getting our hands on a fully functioning production sample.

In our last post, we began the design process for our performance transmission cooler and created a prototype. Thanks to the JL’s cramped cooling stack, our ability to enlarge the transmission cooler was severely limited in the vertical and horizontal planes. However, we were able to significantly increase the thickness of the core from 19mm to 32mm. This 68% increase in core thickness would give the Mishimoto cooler a big leg up on the stock unit, but we couldn’t stop there.

The cramped cooling stack of the JL also means that airflow through the transmission cooler’s core is limited. With less airflow through the cooler, a thicker core won’t be as efficient as it usually would. To counter this problem and make the most of the air passing through the cooler, we decided to construct the core using internal fins. These fins live inside the fluid tubes of the core and serve to add more cooling surface area to the core. These fins also help move the fluid within the tube, ensuring more of it contacts the cooling surface. ...Continue Reading>>>

 

[Mishimoto]

Hey everybody,

Just wanted to let you all know that we're going to start shipping these transmission coolers today, but we'll keep the pre-sale pricing up until tomorrow.

Thank you to everybody who has ordered so far, and if you're still on the fence, today is your last day to order!

Thanks,
-Steve

 

[Yellow Cake Kid]

The 83% increase in fluid capacity amounts to an extra 0.23 quarts.

The other two big numbers;

• 93% increase in external tube area over stock transmission cooler
• 195% increase in internal fin surface area for comprehensive cooling in even the harshest conditions

seem impressive too, but what about the actual performance?

How much cooler does the transmission run with the Mishimoto aftermarket Wrangler JL transmission cooler installed?

Thank you.

 

[rubileon]

The 83% increase in fluid capacity amounts to an extra 0.23 quarts.

The other two big numbers;

• 93% increase in external tube area over stock transmission cooler
• 195% increase in internal fin surface area for comprehensive

seem impressive too, but what about the actual performance?

How much cooler does the transmission run with the Mishimoto aftermarket Wrangler JL transmission cooler installed?

Thank you.

Also I'd like to know if it's better than putting a smaller pusher fan, considering the work and potential warranty issues involved in replacing. The temps are fine when moving so the cooling is needed when stationary which I don't think is best solved by a bigger heat exchanger?

 

[2Wheel-Lee]

Well, I ordered one of these coolers. On a recent wheeling trip. I was driving very aggressively offroad up a windy hill (not a situation that would have been for the faint of heart, for sure!). Basically, I was driving the Jeep as if it were a race vehicle. I'm not exactly sure what happened, but the engine briefly went into a limp mode. Unfortunately, I wasn't in a situation where I had the time to go to the offroad pages to check trans temps, but even when I went to manual mode, it wouldn't let me shift, and I was a speed and engine RPM that should have allowed a shift. I'm guessing the transmission over heated. The conditions I was driving in were certainly extremely hard on the transmission. I backed off the gas for a couple minutes, after which I was able to resume full power. However, the course and speeds also changed, so I was unable to reproduce the problem. I've experienced this once before about 6 months ago under similar tough conditions.

So hopefully this cooler will help reduce the chances of this happening.

I get that no actual testing has been done on the actual cooler - and surely not in the way that I sometimes drive. So we'll see if it really helps. The only variable I do have question about is the change in the inlet/outlet pressures.

 

[2Wheel-Lee]

Also I'd like to know if it's better than putting a smaller pusher fan, considering the work and potential warranty issues involved in replacing. The temps are fine when moving so the cooling is needed when stationary which I don't think is best solved by a bigger heat exchanger?

For practicality sake, I'm not sure how much room there is for another fan in that stack of cooler stuff that's already in there.

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