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

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.

With our design nailed down, we built a prototype and test fit it to ensure our larger cooler would fit in the JL's cooling stack. After a successful test fit, we began building a production sample to test our cooler's performance. A few weeks later, our production sample was finished and ready to test.

Performance testing for our transmission coolers looks a little different than many of our other parts. Instead of installing our transmission cooler on our JL and loading it on the dyno or sending it our for a road test, we hooked it up to our bench test rig. Our bench test rig allows us to control variables that we otherwise could not account for during a road test. We can control ambient temperature in the shop, airflow through the cooler with our dyno fan, the temperature of the transmission fluid, and its flow rate. Keeping all of these variables constant allows us to compare two coolers accurately, without having to worry about traffic or weather skewing our results.

We began our bench test with the stock transmission cooler. Our engineer, Dan, used our bench test rig to heat the fluid to just over 200°F before turning on the pump and allowing the fluid to flow through the cooler. The dyno fan pushed air through the cooler at a steady 20mph (the average speed of air behind the grille at highway speed). Dan watched as the temperature of the fluid at the cooler's outlet dropped. When the fluid reached a steady temperature, we knew the cooler was at its maximum cooling capacity. We then repeated the test with the Mishimoto cooler under the exact same conditions and compared the results.

After crunching the data, we checked the graph and were happy with what we saw. The Mishimoto transmission cooler was able to bring the fluid temperature down to 170°F at the outlet, where the stock cooler was only able to manage about 180°F. Inlet temperatures also dropped significantly compared to stock.

While we were monitoring inlet and outlet temperatures, we were also monitoring pressure drop across the core. The goal here was not to show a lower overall pressure, but a lower drop from the inlet and outlet. When we looked at the pressure graph, we were pleasantly surprised to see that our cooler actually had a lower pressure drop than the stock cooler. The inlet pressures for both coolers were the same, as the inlet size and pump flow rate were the same for both coolers. But what surprised us was how much higher the outlet pressure was for our cooler. This lower pressure drop indicates that our cooler flows better than the stock transmission cooler.

With all of our performance and fitment testing completed successfully, we're confident in our 2018+ Jeep Wrangler JL/2020+ Gladiator transmission cooler. So confident that we're kicking off production and the discounted pre-sale. So, head over to our website for more details and to keep your Jeep's transmission cool, and as always, let us know what you think!

Thanks for reading!