Cooling to the Duramax – Transmission Cooler, Part 3: Adapt and Overcome

This 2001-2014 Chevy / GMC 6.6L Duramax Transmission Cooler is now available! Click here to check it out!

With so many model years to cover, our biggest challenge would be making one cooler fit them all. But we had a plan.

Our 2001-2014 Chevy / GMC Duramax transmission cooler blog so far has focused on the two stock coolers. We looked at the early, comically small, transmission cooler. We looked at the later, and larger but poorly placed, transmission cooler. Finally, after almost a year of R&D, we get to look at Mishimoto’s solution to the stock coolers’ shortcomings. But first, we need to take a closer look at one more of the stock components.


At the end of our last post, we mentioned wanting to use one large cooler to fit all 14 model years from 2001-2014. We also mentioned that doing so presented some challenges. The biggest of those challenges would be to adapt the stock transmission cooler lines to the hose barbs on our stacked plate cooler. With many other trucks, this would be a simple task of determining hose sizes or thread pitch and simply connecting the two together. But the quick-disconnect style of the stock lines, along with the wide range of models, added a layer of complexity.

Before we could tackle the issue of adapting our cooler to the stock lines, we wanted to determine exactly where those lines would lead. For that, we needed to mount our cooler. Luckily, the full range of 2001 to 2014 trucks share a similar U-shaped hoop behind the grille. Mounting our cooler was a simple task of adding four brackets to the core to meet with existing holes in that hoop.


Now would be a good time to mention that we’re using a stacked plate core that’s over 170% larger than the early transmission cooler, and over 40% larger than the largest core offered on the later Duramax trucks.

With our lines’ origin and end points mapped out, we could begin working on connecting the stock transmission lines to our cooler. The challenge would not be in routing the lines, as the distance they needed to cover is a matter of inches on most models, but rather how to adapt multiple variations of quick-disconnects to our hose-barb style fittings. Of course, this was nothing a CNC machine, a block of aluminum, and some clever engineering couldn’t handle.


These little adapters accept stock quick-disconnect fittings and output to a perfectly machined hose barb that mates up to our transmission cooler with a length of transmission cooler hose. They should make installation a piece of cake and even let you use -AN kits already on the market for an even more durable transmission cooler system.

We have our massive transmission cooler mounted and connected to the rest of the cooling system. So, what’s next? Testing. We need to test fit this cooler on each year range and make sure that all that core volume translates into a better cooler. Keep an eye out for our next post!

Thanks for reading,

24 thoughts on “Cooling to the Duramax – Transmission Cooler, Part 3: Adapt and Overcome”

  1. How does this compensate for the temperature of the oil lines that go thru the radiator? Engine temperature can increase trans temp

    1. Hi Tom,

      This cooler replaces the OEM cooler in the same position along the transmission cooling circuit; so the significantly greater efficiency of cooler will be what lowers the transmission fluid temperatures.



    2. When the vehicle is under full load the radiator mounted cooler is doing more cooling than you think due to the heat transfer coefficient of conduction vs convection.

  2. I’ve been following this posting and am very excited. I read that y’all have pushed the release date back to sometime in July or even August. Do y’all have any further information for an update when it will be released? Also, do y’all have a ballpark figure for cost? This is something our trucks have needed for years. Thank you for your time and help.


    1. Hi Russel!

      We’re still aiming for late July or early August for the pre-sale launch, with release in late August or early September. Those dates might move around a little, but that’s our target right now. As for pricing, we don’t quite have a price nailed down yet, but our pre-sale pricing will probably be around $350.



  3. If you would like to have more comparative data, I have a couple different aftermarket coolers to compare it to on our shop truck. I would be glad to help you gather DeltaT and DeltaP differences if you have a prototype to send up here.

    1. Hi Tim,

      Thanks for reaching out, we might take you up on that! I’ll shoot you an email if we do.

      Thanks again!


  4. You should do a package deal for radiator, intercooler, trans cooler, hoses, and heck how about a power steering cooler too. Any plans for a fan in back of the trans cooler?

  5. I’m very excited to hear that the transmission cooler is getting closer to being released. I have a 2002 Chev 3500 dually that I would like to dump a stage 2 Trans in, but I won’t even consider it with the stock cooler.
    Thanks for the updates

    1. Why not Jeremy? A stock cooler is more than capable of handling a built trans.

      I have 30k miles on my built trans without any overheating issues.

      Now mine definitely gets hot (190-200f) but I also just switched to a 3000rpm stall to spool my new setup (S475, 250% overs, built motor ect)

  6. I have recently purchased a 5th wheel trailer and the first trip out we experienced the transmission issue. Not knowing this would be an issue as we have a 2007, 3500 bought in ’09 to pull trailers. We had a 23′ toy hauler before and had no problems with it loaded and ready to go. Now like I had written we have a 5th. 34′ total length and approx. weight (spec) 13500 lbs.(loaded). I had read your article and I am wondering, do I have to make any other changes to the truck, ie: oil cooling, different radiator etc.

    1. Hi Bob,

      You do not need to make any other changes to use our transmission cooler. However, you may need more cooling for the load that your want to haul. The Duramax Forums are a great resource to check out and see what others have done in similar situations.


    1. Hi Jake,

      This pre-sale ended on 8/28, so orders began processing on the 28th. Orders are processed and shipped in the order they were received and our warehouse is a bit behind right now. If you shoot me your last name, I can check on your order and see about expediting it.


  7. Hello,
    I have a 2007.5 2500hd duramax. I had the typical trans cooler line leak so I recently replaced the lines with the fleece heavy duty trans lines kit. (Basically heavy duty hydraulic hoses). I was wondering will your new upgraded trans cooler still work with these fittings? I remember installing them and them being different then stock.

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