Tru Cool 40k Transmission Cooler

Tru Cool 40k transmission cooler LPD47391 and install kit

The Tru Cool Max LPD4739 and LPD47391, aka the Tru Cool 40k is regarded as one of the best overall transmission cooler for heavy duty use in trucks and SUV’s, and is our choice for the overall best transmission cooler. The Tru Cool 40k gets its name from having a GVW (gross vehicle weight) rating of 40,000.

It is very common for drivers who monitor trans temps to see a significant decrease in fluid temperatures after installing this cooler.  The combination of it being an efficient plate and fin style cooler and its overall size help keep transmission fluid cool in even the most extreme conditions. 

Tru Cool 40k With Thermal Bypass

Tru Cool 40k transmission cooler LPD4739 with thermal bypass - Transmission Cooler Guide While both are very similar, there are two different part numbers, the Tru Cool Max  for the Tru Cool Max LPD47391 and LPD4739. The two are designed exactly the same but the LPD4739 utilizes a thermal bypass system within the cooler.

This lets the fluid heat up before it flows throughout the whole cooler.  As fluid warms up it gets thinner, so the colder fluid only flows through the first part of the cooler until it is able to flow better after reaching optimal temperature.

The 40k cooler with thermal bypass is best for drivers who live in colder climates. It is recommended to utilize the stock transmission cooler in the radiator with the Tru Cool Max LPD4739 to allow the fluid to get to a suitable temperature.   While having transmission fluid not get too warm is the goal, it still needs to get warm enough to flow properly through the body of the cooler.

Tru Cool 40k Specifications

Tru Cool 40k transmission cooler LPD47391 - Transmission Cooler Guide

The Tru Cool 40k trans cooler features a highly durable double brazen aluminum construction with precise fin spacing to ensure efficient airflow through the body for maximum cooling. With its 13 rows of cooling, the cooler does a phenomenal job at keeping temperatures in check.

It uses 3/8″ inverted hex flare fitting, which allows for the use of 6 or 8 an lines and fittings for a more secure fit and greater fluid capacity.

Because this cooler is so large and provides extremely efficient cooling capabilities, you can use this as a standalone trans cooler if you so choose.


8 1/2″ x 22″ x 1 1/4″

Gross Vehicle Weight (GVW) Rating:

40,000 pound GVW

BTU Rating:


Fitting Size:

The Tru Cool 40k fitting size is 3/8″ inverted flare hex with 5/8″ thread size –  This is great for those looking to install custom transmission lines

Installation Kit: 

Does the Tru Cool 40k include an installation kit? Yes, it includes universal installation kit with rubber transmission line, various fittings, clamps, and mounting hardware

Tru Cool 40k Transmission Cooler Fittings - Transmission Cooler Guide

Recommended Uses

  • Towing
  • Daily Driven Trucks & SUV’s
  • Performance Trucks & SUV’s

Common Applications

With how big the Tru Cool 40k is, this cooler would be the ultimate trans cooler for those drivers who demand high cooling efficiency.  Many diesel truck owners who tow utilize this cooler to help better control fluid temps. The Tru Cool 40k was on our list of transmission coolers to consider in our towing guide based on its size and how much cooling capacity is offers.

Another common market you will find these coolers used is is within the performance truck realm, especially the Chevy Trailblazer SS, Jeep Cherokee SRT 8, Ford Lightning, or modded full size trucks.

Tru Cool 40k installation on Trailblazer SS - Transmission Cooler Guide

In addition, the Tru Cool 40k is a perfect transmission cooler upgrade for the Cummins, Duramax, and Powerstroke diesel guys as well. Often these trucks see some serious abuse, so this trans cooler is a very viable option for those needing above average transmission cooling.

Since the Tru Cool 40k is such a popular GMC Sierra and Chevy Silverado transmission cooler upgrade on trucks that have 4l60e, 4l80e, or newer 6l80e transmissions, GM full size 1500 and 2500 pickup and SUV owners are fortunate enough to be able to easily mount and install this cooler on their trucks. There are a number of specific Tru Cool 40k Silverado brackets, install, and mounting kits available.  

With how great this cooler is when it comes to keeping temperatures in a safe range, it’s easy to understand why this is the go to transmission cooler for a number of truck or SUV needs.  The Tru Cool 40k is by far on of the best transmission coolers for drivers who demand excellent cooling performance.

Tru Cool 40k Transmission Cooler Installation

tru coo max 40k install on Silverado with brackets and install kit - Transmission Cooler Guide

When installing a transmission cooler, especially the Tru Cool Max 40k, it is important to figure out how much space you have to mount it. Based on its size, the most common area to install the 40k is in front of the radiator. This will provide the most air flow while driving, which will keep temps low.

Most trucks and SUVs have supports that hold the hood latch or stock trans cooler in place. This would be the perfect place to mount the cooler. Since it is much larger than any stock external cooler, you will have to get creative with how you mount the Tru Cool 40k. More often than not, you can get the cooler to fit in this space with some extra mounting hardware.

When considering this cooler as a stand alone (bypassing the stock cooler), it is adequate enough to handle the needs of most applications.  While is it typically recommended to utilize this cooler with the stock radiator cooler, it can certainly be used by itself.

Tru Cool 40k Mounting

There is often debate about installing the Tru Cool 40k and mounting direction. Many will argue that it should be installed either up or down.  Based on past experience, we have never seen any issues with the Tru Cool 40k being mounted down (fittings down).

Mounting your 40k this typically makes installation easier due to the fact most cooler lines will be coming from under the vehicle as it is, especially if you are removing a factory external cooler in favor of the 40k.

What We Like About the Tru Cool 40k Transmission Cooler

  • GVW Rating of 40,000
  • Includes cold weather bypass – Perfect for towing in colder climates
  • Fitting type – The inverted flex flare provides a more secure connection to the transmission cooler lines assuming the right fittings are used
  • Can bypass the stock cooler – This cooler is large enough to use as a stand alone transmission cooler
  • Includes universal installation kit for simple installs.  Kit comes with transmission line, fittings, clamps, mounting hardware

Tru Cool 40k Pros & Cons


  • 40,000 GVW Rating
  • Includes Thermal Bypass (If Needed)
  • Low Pressure Drop System
  • Inverted Flare Fittings
  • Ability To Use As Stand Alone Cooler
  • Includes Universal Install Kit


  • May Be Hard To Fit In Some Vehicles

Tru Cool 40k User Reviews

With the Tru Cool 40k being one of, if not the most commonly used transmission coolers on the market, there is plenty of user feedback to base your purchasing decision on. 

Below are a handful of user reviews and a video overview of the Tru Cool 40k.

"Installed this transmission cooler on my 2016 Silverado 1500 with the 6l80e. Install was easy"
Tru Cool 40k transmission cooler LPD47391 and install kit
Perfect Cooler For GM Truck
"Before I installed this cooler I was seeing 200+ trans temps. After I barely bust 160 in Texas heat"
Tru Cool 40k transmission cooler LPD47391 and install kit
The Only Trans Cooler To Get
"If your in need of a trans cooler, this is the one works great, like no other. Pulling a travel trailer trans temp was always on the rise during 100deg summer in Texas my trans runs pulling trailer 160 deg or below now."
Tru Cool 40k transmission cooler LPD47391 and install kit
Trans Temps At Least 40 Degrees Cooler
The Tru Cool 40k trans cooler kept my transmission at about 180 degrees on a hot day while towing my 28' trailer. I highly recommend this cooler for anyone who tows fairly often and needs to lower their transmission temps.
Tru Cool 40k transmission cooler LPD47391 and install kit
Great Transmission For Any Truck The Tows


Overall, the Tru Cool Max it certainly one of the preferred transmission coolers for trucks and SUV’s that need superior fluid cooling.  Between its size and 40,000 GVW rating, this cooler is certainly capable of handling almost every task.

Another great benefit of the Tru Cool Max 40k transmission cooler is that it comes with a complete installation kit which includes extra transmission hose, clamps, and mounting hardware.  While the kit comes with various fittings, it might be necessary to purchase additional fittings.

For the truck or SUV driver who demands the best, this cooler definitely fits the bill!

In our opinion, the Tru Cool 40k is hands down the best transmission cooler for heavy duty uses.  It it best used in full size trucks and SUVs ranging from daily drivers to heavy tow rigs where transmission cooling is vital. 

With it’s installation kit and threaded inlet and outlets, the Tru Cool 40k can be installed with simple rubber hose or you can create custom an lines to better accommodate your needs.  

Tru Cool 40k

The Tru Cool 40k is a 40,000 GVW transmission oil cooler with a heavy duty plate and fin design that can handle anything without breaking the bank. Get yours today!

Product Brand: Tru Cool

Editor's Rating:


  • 40,000 GVW Rating
  • Includes Thermal Bypass (If Needed)
  • Low Pressure Drop System
  • Inverted Flare Fittings
  • Ability To Use As Stand Alone Cooler
  • Includes Universal Install Kit


  • May Be Hard To Fit In Some Vehicles