Looking to upgrade the transmission cooling capabilities of your Cummins powered truck? You have plenty of options that are both affordable and capable of handing anything you can throw at them.
When it comes to modding your truck, the aftermarket for diesel Rams is nearly limitless, and there are countless options for most areas of your truck, especially when it comes to your transmission. Based on how long transmissions may (or may not) last in your truck it’s important to try to keep temps in check.
Since transmissions can be a weak point in these trucks, it’s always best to keep transmission temps as low as possible, especially if you’ve already swapped in a built trans and converter – need to protect that investment fellas.
With that being said, there plenty of transmission cooler options for your Cummins powered truck, a number of which being direct fit which makes them easy to install.
| Transmission Cooler | Cummins | Price |
 Mishimoto MMTC-RAM-94SL | 2nd Gen | Shop Now |
 Mishimoto MMTC-RAM-03SL | 3rd Gen | Shop Now |
 Mishimoto MMTC-RAM-15SL | 4th Gen | Shop Now |
 Tru Cool Max LPD47391 | Universal | Shop Now |
 Derale 13870 | Universal | Shop Now |
Best 12 Valve Cummins Transmission Coolers
The beauty of the 1st and 2nd gen 12 valve 5.9L Cummins powered Rams is that they are very easy to work on, modify, and are arguably the most reliable diesel used in a pickup truck.
The impressive reliability of the 12 valve Cummins comes from them being extremely basic engines that didn’t have any modern technology or electronics or emissions control. The fact that everything was mechanical makes it almost bulletproof.
With that being said, the 1st gen Cummins’ were equipped with either a 3-speed A727 or 4-speed 46RH transmission with overdrive from 1989-1993 , and the 2nd gen 12 valve came backed by a 47RH 4-speed.
When it comes to automatic transmission cooler options for the 1st and 2nd gen Cummins, there aren’t many direct fit options, but of the truck specific kits available, they are extremely easy to put in. Because of this, we recommend some of the best universal transmission cooler that you can install on your truck that are great for both daily drivers or something that might face more extreme conditions or situations such as towing, racing, or even sled pulling.
Here are our top transmission cooler picks for your 1st and 2nd gen Cummins:
- Tru Cool 40k
- Derale (Remote mount with Fan)
- Mishimoto MMTC-RAM-94SL
1st Gen Cummins Transmission Coolers
Like previously stated, the 1st gen 12v Cummins powered Ram is a simple truck that requires very little in terms of maintenance and is very easy to modify. When it comes to upgrading the transmission cooler on your 1st gen, there is no direct fit option, but plenty of universal kits that can handle what you need.
Between the Tru Cool 40k and Derale 13870, you can keep transmission temps in a safe range and prevent transmission damage due to over heating. As we all know, heat is the #1 killer of transmissions, and these coolers do an excellent job of keeping temps low.
Tru Cool 40k
As mentioned a number of times before, the Tru Cool 40k has been our choice for the best overall transmission cooler for all kinds of trucks. Just like its name indicates, this cooler is rated at 40,000 GVW, which is more than enough to handle most tasks.
So whether you are using your 1st gen as a fun cruiser, towing or hauling heavy loads, or more, this cooler is capable of keeping trans temps nice and cool.
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 best universal transmission cooler for trucks. Learn more about the Tru Cool 40k transmission cooler.
Shop Tru Cool 40k
Get the lowest price on Tru Cool 40k transmission coolers and lower your transmission temps today!
Shop NowDerale 13870
Derale 13870 Specs
If you use your truck for more than day to day activities and need more cooling efficiency, then look no further than the Derale 13870. To put it frank, this is a no BS, will take all you can dish out and then some transmission cooler.
This cooler can be mounted remotely under the bed or along the frame rails, making for a fairly simple installation. With it’s 800 cfm fan, the Derale 13870 will definitely stay cool in all conditions.
Including its fan, the Derale 13870 measures 14 7/8″ x 13″ x 5 5/8″ which considering its size, still allows you to mount it remotely in tight spaces. This cooler is not designed to be used in front of a radiator or condenser unless there have been modifications made and there is ample room.
This cooler comes standard with female threads at the inlet and outlet of the cooler which allows for various size fittings to be used. There are options to use -6an, -8an, -10an, or even up to-12an fittings. Because of this, there is serious flow through the cooler to reduce temps fast.
Cooler Dimensions: 14 7/8″ x 13″ x 5 5/8″
Fitting Size: -6an, -8an, -10an, or -12an
Number of Cooling Rows: 40
Fan Size: 10″
Fan Specs: 800 cfm – water and dustproof
Read our complete Derale 13870 transmission cooler write up here.
Shop Derale 13870
Get the lowest price on Derale 13870 transmission coolers and keep your 1st gen Cummins running like it should!
Shop Now2nd Gen Cummins Transmission Coolers
The 2nd gen Cummins Ram (94-02) is still one of the most highly sought after diesel trucks on the market, especially a clean one with the 12v. The beauty of the 2nd gen is that they plenty of aftermarket options for practically every part on the truck, including transmission coolers.
Mishimoto MMTC-RAM-94SL
Mishimoto is an industry leader in fluid cooling solutions, offering some of the highest quality parts on the market. The MMTC-RAM-94SL is no different. This cooler was designed as a 100% direct fit for your 94-02 2nd gen Cummins Ram.
This cooler offers a transmission fluid capacity increase of 141% and a total core volume increase of 116%. Simply put, this cooler will keep your 2nd gen’s transmission much cooler than the factory setup ever will.
Mishimoto MMTC-RAM-94SL Specs
Cooler Dimensions: 16.8″ x 8.5″ x 1.4″
Fluid Capacity: 0.66 quarts
Installation Kit: 29.5″ transmission hose, barb fittings, worm clamps, mounting hardware
3rd Gen Cummins Transmission Coolers
Available from 2003 to 2009, the 3rd gen Cummins Rams are one of the most desirable modern diesel trucks due to still being able to get the 5.9L 24 valve Cummins paired with newer technology and modern space in the cabin.
The 3rd gens featured high-pressure common rail fuel injection which helped in making these trucks more efficient than the earlier generations.
In 2007.5 the 6.7L Cummins took the place of the 5.9L in an effort to lower emissions. While some people were on board with this change, enthusiasts were hesitant and would rather keep the older 5.9L.
With the change in engines, all 3rd gens also swapped transmission from the 48RE 4 speed transmission behind the 5.9L to a 68RFE behind the 6.7L. As many Cummins owners know, the both the 48RE and 68RFE can be a good transmissions when used at near stock power, but when more power is added, there are a few common issues.
When it comes to keeping the 48RE or 68RFE in your 3rd Gen Cummins shifting and working like it should, it is always a good idea to add an external transmission cooler to lower trans temps. Here is our top pick for best 3rd gen Cummins transmission cooler.
Mishimoto MMTC-RAM-03SL
Specifically designed for the 03-09 5.9/6.7L Cummins, the MMTC-RAM-03SL offers a transmission fluid capacity increase of 244% and a total core volume increase of 212%. Compared to other direct fit transmission coolers, this one is one of the largest available and receives more than enough airflow to keep trans temps in check.
In addition, the MMTC-RAM-03SL includes a bypass for the transmission thermostat. Bypassing the thermostat helps keep fluid flowing through the cooler constantly without reaching a certain temperature like the factory setup does.
Overall, this transmission cooler is one of the best available for your 5.9 or 6.7L 3rd gen Cummins.
Mishimoto MMTC-RAM-03SL Specs
Cooler Dimensions: 26″ x 10.94″ x 0.87″
Cooling Rows: 48
Fluid Capacity Increase: 0.88 quarts
Fitting Type: 3/4″-16 SAE Barb
Installation Kit: transmission hose, fittings, worm clamps, thermostat bypass
4th Gen Cummins Transmission Coolers
Available from 2010 to 2018, the 4th gen Cummins Rams featured plenty of new technology and features not available in previous generations. In addition to new features, the 4th gens were equipped with 2 different automatic transmission depending on the year.
All 4th gen Cummins’ were backed by the same 68RFE found in the later year 3rd gens up to 2013 until the Aisin 6-speed auto was used in dually applications.
While there only seems to be 1 direct fit transmission cooler for the 4th gen Cummins, you can easily use one of the universal coolers we had mentioned earlier to help keep your trans temps in check.
Mishimoto MMTC-RAM-15SL
Specifically designed for the 15-18 6.7L Cummins, the MMTC-RAM-15SL utilizes a highly durable plate and fin construction that provides serious cooling capacity. This cooler increases fluid capacity 226% with an increased surface area of 237% overall.
Like other Mishimoto coolers mentioned, this cooler is a direct fit for your truck and requires 0 modification or any sort of fabricating of brackets to make it fit. The MMTC-RAM-15SL includes all necessary installation hardware and mounting pieces to make it a seamless installation that can be done in your driveway. .
Overall, this transmission cooler is the best direct fit cooler for your later 4th gen Cummins.
Mishimoto MMTC-RAM-15SL Specs
Cooler Dimensions: 24.76″ x 11.85″ x 1.25″
Fluid Capacity Increase: 0.76 quarts
Installation Kit: transmission hose, fittings, worm clamps, thermostat bypass
