Which fluid should never be installed in a manual transmission?

A manual transmission is specifically designed to operate with certain types of fluids that provide the necessary lubrication and protect the internal components from wear. Using the appropriate fluid type is crucial for ensuring optimal performance and longevity of the transmission.

Brake fluid is hydrophilic, meaning it absorbs moisture, which can lead to corrosion and internal damage within the transmission system. Furthermore, brake fluid does not possess the proper lubrication properties that gear oil or transmission fluid have. Transmission systems require fluid that can withstand high pressures and temperature variations while also providing sufficient lubrication to prevent metal-to-metal contact.

In contrast, gear oil is specifically formulated for the needs of a manual transmission, offering the necessary viscosity and protective qualities. Similarly, transmission fluid is designed to meet the specific requirements of the transmission system, providing optimal performance under various driving conditions. Motor oil, while it may appear suitable due to its lubrication qualities, is not formulated to handle the stress and demands of a manual transmission.

In summary, brake fluid should never be installed in a manual transmission due to its potential to cause damage through moisture absorption and lack of suitable lubrication properties.