What Size are Transmission Cooler Lines

Transmission cooler lines are usually between 1/4 inch and 5/16 inch in diameter. The size of the transmission cooler lines depends on several factors including the amount of fluid being cooled, the temperature range that needs to be maintained, and any space constraints. Thicker lines will provide more cooling capability but can take up more space under the hood or in a transmission pan.

It is important to use properly sized transmission coolers for optimal performance as too large a line may cause pressure drops resulting in poor cooling efficiency.

The size of transmission cooler lines can vary depending on the type and model of vehicle you have. Generally, standard transmission coolers are equipped with 3/8 inch or 5/16 inch diameter lines, while larger vehicles may require 1/2 inch or even 5/8 inch diameter tubing. It is important to check your owner’s manual for the correct size line that should be used for your particular vehicle.

In addition to the size of your transmission cooler lines, you must also consider the length in order to ensure efficient cooling performance.

Help! Transmission Cooler line leaking?


What is the Diameter of a Transmission Cooling Line?

The diameter of a transmission cooling line will vary depending on the make and model of your vehicle. Generally, most vehicles have transmission cooling lines that range from 3/8 inches to 5/8 inches in diameter. The larger the engine size and torque output, the larger the transmission cooling line will need to be so that it can provide sufficient flow for heat dissipation.

It is important to ensure you are using an appropriately sized coolant line when replacing or upgrading your existing system as using too small a diameter could lead to overheating issues.

What Size is Gm Transmission Cooler Lines?

GM transmission cooler lines come in a variety of sizes, depending on the model and year of your vehicle. Generally speaking, most GM vehicles have either 3/8” or 5/16” line size for their transmission coolers. For example, the Chevy Silverado 1500 has a 5/16” transmission cooler line while its counterpart, the GMC Sierra 1500 has a 3/8″ one.

Before purchasing replacement lines for your vehicle’s transmission cooler system it is important to double check the exact size you will need so that they fit properly with no leakage issues.

What Size is Transmission Cooler Fitting on Radiator?

The size of the transmission cooler fitting on a radiator will vary depending on your specific make and model. Generally, most aftermarket radiators have an 1/8-inch NPT male thread for the transmission cooler line connection. Some vehicles may require a different size fitting, so it is important to check your vehicle’s manual before making any modifications.

Additionally, you should also consider whether you need an adapter to fit between the radiator and transmission cooler lines in order to ensure compatibility with your particular car or truck.

What Kind of Hose Do You Use for a Transmission Cooler?

When selecting a hose to use for a transmission cooler, it is important to use one that can handle the pressure and temperature of your vehicle’s transmission fluid. The best type of hose to use for this purpose is an SAE J1532-rated hose, which is designed specifically for high-pressure automotive applications. This kind of hose will provide superior durability and strength compared to other types of hoses, ensuring that your transmission fluid stays where it’s supposed to without any leaks or cracks in the line.

Additionally, these hoses are resistant to oil and coolant spills as well as abrasion from engine heat and vibration. For optimal performance, make sure you choose an SAE J1532-rated hose when replacing or installing a new transmission cooler on your vehicle.

What Size are Transmission Cooler Lines

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Can I Use Rubber Hose for Transmission Cooling Lines

Using rubber hoses for transmission cooling lines is not recommended. Rubber hoses are not rated to handle the high temperatures and pressures of a transmission system, which can cause them to become brittle and crack over time. In addition, rubber hoses do not provide adequate vibration dampening protection that metal lines offer.

For these reasons, metal lines are the preferred choice for transmission cooling systems as they will last much longer and provide better performance in the long run.

Gm Transmission Cooler Line Size

GM transmission coolers require specific line sizes to ensure a safe and effective cooling system. The cooler lines should be 5/16” in diameter or larger, with 3/8″ being the most common size found on GM vehicles. It is important that these cooler lines are properly sized to facilitate efficient heat transfer from the fluid to the air, otherwise your transmission may overheat and fail prematurely.

Nylon Braided Hose for Transmission Lines

Nylon braided hose is a great option for transmission lines, as it offers superior flexibility and durability. It’s made from nylon, which is an incredibly strong material that can withstand extreme temperatures, vibration and pressure. Additionally, the braided design helps to increase its resistance to wear and tear over time.

As such, these hoses are ideal for any automotive application where reliability and performance are critical.


This blog post provided a detailed overview of transmission cooler lines, their sizes, and how to select the right size for your vehicle. It is important to remember that selecting the correct size for your application is essential for proper cooling and performance. Furthermore, it is always recommended to consult with a professional before making any changes or modifications to ensure you get the best results from your transmission cooler lines.

With this knowledge in mind, you can now make an informed decision about what size transmission coolers lines are needed for your vehicle.


  • Alex Gearhart

    Alex Gearhart, an automotive expert specializing in transmissions, has over a decade of hands-on industry experience. With extensive knowledge in manual and automatic systems, Alex is passionate about educating car enthusiasts on vehicle maintenance. As the chief author at TransmissionCar.com, Alex simplifies complex concepts for readers, helping them make informed decisions about their vehicles. Outside of work, Alex enjoys road trips, restoring classic cars, and exploring new automotive technologies.

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