Strength of Heart – Transmission Cooler R&D, Part 1: Stock Review

If you ask most drivers what the heart of their vehicle is, they’ll likely say the engine. The engine provides power and is often the most advertised part of the powertrain, but it’s not alone. In fact, if you ask somebody who tows heavy loads, they might say the heart of their car or truck is the transmission. A vehicle’s transmission is responsible for delivering all the power the engine makes to the wheels, and its success or failure in that role can make or break the vehicle, especially when towing. Few drivers know the importance of a well-designed transmission better than owners of 6.7L Cummins-powered RAM trucks and the engineers at Mishimoto.

We also know that it doesn’t matter how well-designed a transmission is if you can’t keep it cool. Over the years, we’ve developed transmission coolers for nearly every iteration of Cummins-powered RAM; now, it’s time to apply that experience to one of the latest generations with a performance transmission cooler for the 2015-2018 6.7L Cummins Dodge RAM. To begin development, we’ll first analyze the stock cooler.

Transmission coolers on RAM trucks often swing between two extremes. Some, like the 1994-2002 transmission cooler, are simple tube-and-fin coolers with an inlet, outlet, and not much in between. Others, like the 2003-2009 transmission cooler, include complex parts like integrated thermostats. No matter how different they may be, however, all of them share one thing: they can be improved. To find out where the 2015-2018 transmission cooler fell in that spectrum, we pulled our volunteer truck into the shop and began R&D.

Our engineer, Jason, popped the hood and started making his way to the transmission cooler. Between the A/C condenser and the radiator, Jason found a pleasant surprise. The 2015-2018 RAM Cummins transmission cooler follows the model set by its earlier relatives, opting for size and simplicity over complexity. There are no internal thermostats to replicate or intricate lines to consider. The stock cooler is a simple, thin, tube-and-fin design with an inlet on one side and an outlet on the other. It doesn’t get more basic than that.

Like most stock heat exchangers, the 2013-2018 RAM Cummins transmission cooler was built to meet a budget and leaves a lot to be desired. Despite being crammed between the A/C condenser and the radiator, the stock transmission cooler has room to grow in all directions. The simple mounting tabs mean that we’ll be able to enlarge the core significantly, without worrying about modifying the mounts. Simply making the core larger will substantially improve the performance of the cooler, but we’re not going to stop there. To make the most out of the available space, we’ll test different fin and tube variations to find the best balance between flow and cooling capability.

In the next post, we’ll be designing our performance transmission cooler and creating a prototype to test fit. So, keep an eye out for more updates and, as always, let us know what you think.

Thanks for reading,
-Steve

3 thoughts on “Strength of Heart – Transmission Cooler R&D, Part 1: Stock Review”

  1. Please keep me updated. I have a 2017 Ram, 6.7 Cummins and tow heavy loads. I would like to increase transmission cooling to extend its life. When not towing transmission temps run about 165F, but when towing they reach 185F to 190F. I would like to keep these temps below 170F. In addition, the air conditioning condenser sucks in this truck. The air conditioning only works well when moving more that 60MPH. The condenser appears to be about half the width of the one in my Ford Powerstroke which you can hang meat in, even when stopped at idle. The R134 charge is correct, it is just to small of a system to get the job done well. May be while you are work on this truck you can evaluate the condenser coil as well. Just wishing!

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