Excess heat is the bitter rival of any vehicle, but especially when it comes to heavy-duty trucks, like the 2015+ 6.6L Duramax powered Chevys and GMCs. The HD Silverado and Sierra are already mega heat-generating machines on their own. Still, GM designed these trucks for the express purpose of pulling, towing, hauling heavy payloads, and generating even more heat. While you might have opted for the Heavy-Duty Duramax powerplant, the engine is only half of the equation. No matter if you chose to upgrade to the coveted Allison gearbox or not, the transmission is the other half of what slots these trucks into the Heavy-Duty category. Keeping those gears at prime operating temperature is vital and exactly what we have in mind.
GM also had the same thought and has been including an external transmission cooler on all their trucks since at least 2001. Like the coolers found installed on the previous models, the cooler equipped on the LML and L5P is adequate. In most typical driving conditions, you won’t need to hyper-focus on the transmission temperature readout. However, some will have experiences where that might not be the case. Luckily, there’s plenty of room for improvement in the Duramax’s transmission cooling system.
When we say plenty of room to expand, we meant it. Given this truck’s primary function, we felt that it needed a transmission cooler that stacks up to its HeavyDuty moniker to provide a heavy-duty amount of cooling. Our new cooler utilizes a stacked plate core, meaning that it’s tough enough to perform no matter what’s thrown at it. Also, if you couldn’t tell from the photo above, it’s much bigger. Specifically, we added 67% to the cooler’s core volume, allowing for an overall increase in fluid capacity and cooling efficiency. The larger core also means a massive 164% jump in external fin surface area, which is crucial for heat transfer.
Since we’re expanding the size of the core beyond the stock perimeters, that means our cooler won’t fit in the bumper cutout that Chevy worked into their bumper design for the transmission cooler. So, we opted for relocating our cooler to the main grill since there is plenty of open real estate. For this move, we drew inspiration from our K2 cooler and employed our radiator support clamps to mount the core. These clamps provide a secure mounting solution without us needing to chop up any parts of your radiator support.
This relocation also means that the transmission fluid lines will also need some redirection. Again, we drew inspiration from our past GM truck experience (this time from the previous Duramax transmission coolers) and devised a set of CNC-machined adapters that mate perfectly with the factory hardlines and redivert the fluid flow up to the cooler’s new location.
When it comes to these Heavy-Duty trucks, bigger is better. The bigger the truck, the bigger the payload capacity, but also the bigger the cooling needs. Luckily, our new LML and L5P cooler kits are up to the task. Make sure that you get yours today:
Thanks for reading!