DIY Replacement Chevy Transmission Cooling Lines

by Lauren Treadwell

Chevrolet truck transmission cooler lines keep your transmission from overheating during hot summer days when you're stuck in traffic with the air conditioning blasting. They transport the automatic transmission fluid away from the hot gears of the transmission. The fluid cools slightly during the movement through the lines before returning to the transmission. Without such a cooling mechanism, the transmission fluid can become extremely hot and cause the Chevy's transmission to break down.

Functions of the Cooling Lines

When automatic transmission fluid gets to a certain temperature, its viscosity changes and the liquid thins considerably. The fluid no longer properly lubricates the transmission's moving parts, and the Chevy's gears can either stick or not shift at all. As a lubricant, the transmission fluid also cools the transmission to keep it from warping and bending.

The cooling lines help the fluid to chill by removing it from the hot transmission and allowing it to pass through a cooler zone. This cooling also prolongs the life of the fluid. However, like all tubing in the car, the transmission cooling lines can leak, causing the transmission to overheat and fail if you do not replace the lines immediately.

Buying Cooling Lines

Buy cooler lines that are designed for your Chevy model. Chevy trucks require two separate lines--a feed line and a return line--that are bent into certain shapes to fit the underside of the truck. While standard brake lines can be modified to fit the Chevy, they are usually too short for the job and require extensive rerouting of the transmission cooler lines.

Most standard cooler line sets for Chevrolet vehicles are available for less than $30, and replacement connectors are generally available for less than $20. If you want the most efficient cooling system for your transmission, consider adding a second cooler in addition to the factory-installed one. This will ensure that your automatic transmission fluid never becomes too warm, prolonging the life of the entire transmission considerably.

Replacing Cooling Lines

Since the disconnected lines will likely weep fluid, place a drop cloth on the ground after raising the Chevy with a jack. Drain the transmission fluid into a pan and reserve it to replenish the system afterward. After locating and removing the existing cooling lines from the transmission and then the radiator, verify that they match the replacements exactly. Since hard tubing is more prone to leaks if bent excessively, it is important to bend the tubing as little as possible to maintain the original shape.

Install the top line first to avoid blocking access to it with the lower line. Finally, install the bottom line and tighten all the connections with an adjustable torque wrench. Refill the transmission fluid, and test the lines for leaks before driving the Chevy.

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