Need to upgrade the transmission cooling capabilities of your Duramax powered truck? Don’t worry, we have solutions.
The Duramax diesel is backed by an Allison transmission, which is found in heavy duty GM trucks designed for towing and hauling heavy loads. Not only that, but it makes for a fun street truck as well. When it comes to towing, hauling, or simply having fun, you need to keep your truck cool.
When considering transmission coolers for your Duramax, there are a number of options, both universal and direct fit depending on the year of your truck.
Here are some of our recommended Duramax transmission cooler upgrades!
Note: Looking for transmission coolers for a gas GM truck? Check out our Silverado & Sierra Transmission Cooler Guide.
| Transmission Cooler | Duramax | Price |
 Mishimoto MMTC-DMAX-01SL | LB7 | Shop Now |
 PPE Performance 124060000 | LB7 | Shop Now |
 Mishimoto MMTC-DMAX-03SL | LB7 / LLY (03-05) | Shop Now |
| PPE Performance 124060300 | LB7 / LLY (03-05) | Shop Now |
 Mishimoto MMTC-DMAX-06SL | LBZ / LMM (06-10) | Shop Now |
 Tru Cool Max LPD47391 | Universal | Shop Now |
 BD Diesel 130061 | Universal | Shop Now |
LB7 Duramax Transmission Coolers
The LB7 6.6L V8 Duramax was used in 2001 – mid-2004 model trucks, replacing the far less powerful 6.5L Detroit Diesel. The Duramax was far superior in every way possible, making these trucks highly sought after.
With the new power plant, GM diesel truck owners quickly found out that the LB7 is capable of moving serious weight with ease.
When it comes to getting the wheels in motion, the LB7 relies on an Allison transmission to transfer power to the ground. These transmissions can handle some power, but could still use some assistance in terms of transmission cooling.
Based on this, here are our top picks for the best transmission coolers for your LB7 Duramax.
Mishimoto MMTC-DMAX-01SL
Mishimoto is an industry leader in fluid cooling solutions, offering some of the highest quality parts on the market.
They take pride in their ability to fabricate direct fit components for many vehicles, including LB7 equipped trucks.
The Mishimoto MMTC-DMAX-0 1SL is designed to be a 100% bolt in transmission cooler, making the installation flawless. All Mishimoto Duramax transmission coolers come with all the necessary lines, brackets and fittings to complete the installation.
Mishimoto MMTC-DMAX-01SL Specs
Cooler Dimensions: 29″ x 14″ x 4″
GVW: 40,000 pounds
BTU Rating: 45,000
Fitting Size: 3/8″ inverted flare hex with 5/8″ thread size – This is great for those looking to install custom transmission lines
Installation Kit: Yes – Includes universal installation kit with rubber transmission line, various fittings, clamps, and mounting hardware
PPE Performance 124060000
With a 60% larger surface area compared to a factory Duramax transmission cooler, the Pacific Performance Engineering (PPE) Performance 124060300 transmission cooler is a great option for your LB7.
This cooler comes with installation brackets and hardware to make it a 100% complete bolt in transmission cooler kit for your truck. PPE claims this cooler will easily lower trans temps up to an additional 20 to 30 degrees over the factory cooler when towing.
This cooler is identified as having purple clips, and is designed for 2003-2005 trucks, and installation of this kit is extremely easy. Since this is a 100% complete kit, installation should take an hour or less for the average DIY truck owner.
PPE Performance 124060000 Specs
Cooler Dimensions: 14.18″ x 7.65″ x 1.87″
GVW: 40,000 pounds
Cooling Rows: 24
Fitting Size: 3/8″ inverted flare hex with 5/8″ thread size – This is great for those looking to install custom transmission lines
Installation Kit: Yes – Includes all necessary mounting hardware and brackets.
LLY Duramax Transmission Coolers
The LLY is the 2nd generation Duramax that was produced from mid-2004 – late 2005. This Duramax was backed by the same 5 speed Allision 1000 transmission that the LB7 Duramax came equipped with.
While the LLY and LB7 trucks are similar, their transmission coolers have some differences. Here are our choices for transmission coolers for your LLY.
Mishimoto MMTC-DMAX-03SL
As you can see, we are a big fan of Mishimoto direct fit transmission coolers. Not only do they make installation super easy, but they perform better than most. Similar to the MMTC-DMAX-01SL for the LB7 trucks, the LLY trucks have their own cooler. The two coolers look similar, but there is a slight difference.
The Mishimoto MMTC-DMAX-03SL transmission cooler kit works with 2003+ trucks that have purple clips, whereas the MMTC-DMAX-01SL is designed for earlier trucks with orange clips.
The Mishimoto MMTC-DMAX-03SL is designed to be a 100% bolt in transmission cooler, making the installation simple with basic hand tools.
Mishimoto MMTC-DMAX-03SL Specs
Cooler Dimensions: 29″ x 14″ x 4″
GVW: 40,000 pounds
BTU Rating: 45,000
Fitting Size: 3/8″ inverted flare hex with 5/8″ thread size – This is great for those looking to install custom transmission lines
Installation Kit: Yes – Includes universal installation kit with rubber transmission line, various fittings, clamps, and mounting hardware
PPE Performance 124060300s
With a 60% larger surface area compared to a factory Duramax transmission cooler, the Pacific Performance Engineering (PPE) Performance 124060300 transmission cooler is a great option for your LB7.
This cooler comes with installation brackets and hardware to make it a 100% complete bolt in transmission cooler kit for your truck. PPE claims this cooler will easily lower trans temps up to an additional 20 to 30 degrees over the factory cooler when towing.
This cooler is identified as having purple clips, and is designed for 2003-2005 trucks, and installation of this kit is extremely easy. Since this is a 100% complete kit, installation should take an hour or less for the average DIY truck owner.
PPE Performance 124060300s Specs
Cooler Dimensions: 14.18″ x 7.65″ x 1.87″
GVW: 40,000 pounds
Cooling Rows: 24
Fitting Size: 3/8″ inverted flare hex with 5/8″ thread size – This is great for those looking to install custom transmission lines
Installation Kit: Yes – Includes all necessary mounting hardware and brackets.
LBZ & LMM Duramax Transmission Coolers
The LBZ Duramax was produced from late 2005 until 2007, and only put into “classic” style trucks. Compared to the LLY that precedes it, the LBZ had improved tuning capabilities that helped produce more power and torque.
Like earlier models, the LBZ Duramax came equipped with the Allison 1000 6-speed transmission
The LMM Duramax made its debut in late 2007 in the new body style trucks and was also backed by the Allision 1000 6-speed.
Despite the truck, the LBZ and LMM Duramax have transmission coolers that will help keep that Allision 1000 cool whether you are towing, hauling, or just cruising.
Mishimoto MMTC-DMAX-06SL
Once again, Mishimoto offers a direct fit transmission cooler. The Mishimoto MMTC-DMAX-06SL is specifically designed to work with your 2006-2010 LBZ / LMM Duramax.
Just like the previous transmission coolers mentioned before, The Mishimoto MMTC-DMAX-06SL is a 100% bolt in transmission cooler. This cooler like other Mishimoto cooler is extremely easy to install and with basic hand tools, you can get the cooler on your truck in an hour or so.
Mishimoto MMTC-DMAX-06SL Specs
Cooler Dimensions: 29″ x 14″ x 4″
GVW: 40,000 pounds
BTU Rating: 45,000
Fitting Size: 3/8″ inverted flare hex with 5/8″ thread size – This is great for those looking to install custom transmission lines
Installation Kit: Yes – Includes universal installation kit with rubber transmission line, various fittings, clamps, and mounting hardware
Universal Transmission Coolers
Interested in a universal transmission cooler that give you the freedom to plumb your own lines and fittings? Don’t worry, we’ve got you covered!
Here are our top picks for the best universal transmission coolers for your Duramax.
Tru Cool 40k
The Tru Cool 40k has been our choice for the overall best transmission cooler, and rightfully so. This cooler is rated at 40,000 GVW, which is enough to handle the most strenuous tasks.
Like reviewed in our Silverado and Sierra 1500 transmission cooler guide, the Tru Cool 40k has a large aftermarket for most late model GM trucks. It is not hard to find an installation kit specific for these trucks, making install a breeze.
So whether you are towing or hauling heavy loads, this cooler is certainly up for the challenge.
Tru Cool 40k Specs
This cooler is designed with a large large plate and fin construction that has 13 cooling rows. Due to its overall large size and design, the Tru Cool 40k is a great option for your Duramax powered truck.
Cooler Dimensions: 8 1/2″ x 22″ x 1 1/4″
GVW: 40,000 pounds
BTU Rating: 45,000
Fitting Size: 3/8″ inverted flare hex with 5/8″ thread size – This is great for those looking to install custom transmission lines
Installation Kit: Yes – Includes universal installation kit with rubber transmission line, various fittings, clamps, and mounting hardware
For the money, the Tru Cool 40k is hands down one of, if not the go-to universal transmission cooler for trucks. Read our full write up of the Tru Cool 40k transmission cooler.
BD Diesel 1300611 Transmission Cooler With Fan
The BD Diesel 1300611 transmission cooler will provide your Duramax with excellent cooling. With its 800 CFM 12″ fan, this cooler will be sure to keep your temps as low as possible.
Depending on your setup, this cooler can be mounted remotely or right behind the grille like standard applications.
See our full BD Diesel 130061 review here.
BD Diesel 130061 Specs
Cooler Dimensions (Including Fan): 17.5″ x 15.5″ x 7.4″ (including fan)
Fitting Size: -10an
Type of Cooler: Plate & Fin
Cooling Rows: 25
Fan Size: 12″
Fan Specs: 800 CFM
GVWR: 30,000 (33,930 BTU)
