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How to Upgrade Your Duramax Transmission Cooler in 8 Easy Steps

A Common Repair Made Quickly and Easily

When it comes to diesel engines (towing with them especially), the No. 1 enemy of any component is heat. This is especially true when it comes to your transmission. Unlike coolant, transmission oil temperatures move slowly. This is great for warming up, but this also means that once your fluid is heat soaked, it takes longer to cool down. The factory transmission cooler in your Duramax truck may be fine for a stock application, but adding things like bigger wheels and tires can add additional rolling resistance and thus more friction. More friction means more heat and, well, nobody likes cooked transmissions now, do they?

 

The folks over at DmaxStore.com have it covered when it comes to transmission coolers with the company’s Maxflow Arctic series coolers. This cooler design has been on the market for a bit now with great results, but the team at DmaxStore just did a refresh and added a few key features that might make this one the best coolers for your money.

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Step 1: Installing this cooler is a breeze (pun intended) and only took us about an hour total. We started by removing the plastic core support cover on the truck using a plastic pry tool to pop out the various plastic retainer clips that hold this in place. After that, we removed the grille by popping out the retainer clips and setting them off to the side. This gave us access to the transmission cooler and left plenty of room to get the old one out.

Step 2: Up next, we removed the C clips that hold the transmission cooler lines in place. One unique thing about the DMaxStore Arctic Flow trans cooler is that it comes with all-new clips. This is huge, as anyone who has taken off one of these clips knows that it’s really easy to launch them across the shop, and if you’re not careful, you’ll lose them. Once the clips were off, we gently wiggled the lines until they came free, being careful not to pry too hard on the metal lines.

Step 3: Once the lines were off, we moved to the two mounting bolts for the transmission cooler. These 10mm bolts are easily removed with an electric ratchet if you have one. Once the bolts were removed, we pulled the transmission cooler out and set it aside.
Step 4: As you can see, the new DmaxStore transmission cooler is much bigger than the factory one. In fact, according to DmaxStore, this new trans cooler is 66% thicker than the OEM cooler. This equates to more surface area, which will help keep your transmission cooler.

Step 5: Before we could mount the new transmission cooler, we needed to get the brackets set up for proper orientation. These brackets come pre-installed on the cooler in a way that places them inward, preventing damage to the mounting tabs during shipping. We  simply flipped that bottom bracket around, installed the top brackets with the included hardware, and added the rubber isolators to the bottom bracket, and we were good to go. Pro tip: If you’re in a climate where there’s salt or other corrosion, buy the optional stainless hardware. It will keep your trans cooler hardware from corroding, making your life easier down the road.

Step 6: The last step before we installed the cooler was to lube up the O-rings on the inside of the push-to-connect fittings. This is going to ensure that our new transmission cooler doesn’t leak after we install it. Once that was done, we installed the new cooler into the truck with the factory bolts and pushed our lines into the new cooler. The C clips can be left in place in the fittings as they will expand and then snap down into place on the lines once you’ve seated them properly. As always, once you’ve installed the lines, give them a gentle tug to ensure they’re seated properly into the cooler and you’re all set.
Step 7: Finally, we topped off the transmission fluid as the new cooler will take a bit more fluid than the factory one and you have lost some with the old cooler. We topped it off, let the truck get up to temperature, and checked the fluid on the dipstick according to the owner’s manual.

Step 8: And there you have it—a much needed upgrade for any Duramax owner who tows on the regular. I noticed almost immediately that my transmission stayed cooler longer. It also allowed the fluid temperatures to cool off much more rapidly versus my factory cooler. If you’re interested in picking up one of these coolers make sure you check out the folks at DmaxStore.com!

PHOTO BY RYAN SINKLER

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