How Does Transmission Fluid Go Bad in a Sealed System?
Understanding the workings of a transmission system can be complex, especially when considering the lifespan of transmission fluid in a sealed environment. Contrary to popular belief, the fluid can degrade over time due to several factors, even within a seemingly airtight system. The primary cause of fluid breakdown is not mechanical wear but rather shear failure, a process that leads to the chopping of long hydrocarbon chains into shorter ones. This article will explore the various factors contributing to the degradation of transmission fluid within a sealed system, including shear failure, heat, contaminants, additive depletion, and moisture.
Shear Failure: The Main Cause of Transmission Oil Wear Out
The primary reason for transmission oil degrading in a sealed system is shear failure. This process occurs when the long hydrocarbon chains of the oil are chopped into shorter chains through friction, particularly in the torque converter and between metal faces such as gears. The cut ends of these chains can recombine inappropriately, resulting in thinner oil that loses its ability to protect against wear effectively. In some cases, these cut chains can cross-link, forming much thicker materials that eventually solidify, such as varnish.
To address this issue, fully synthetic oils are engineered with chemically uniform chains that do not have cross-linking sites or fragile links that break easily. These oils can remain effective for more miles than conventional oils or synthetic oils that are treated to become super-refined and not chemically uniform.
Common Factors Contributing to Transmission Fluid Degradation
Heat
Even in a sealed transmission system, the fluid operates at high temperatures, which can cause it to chemically break down, a process known as oxidation. Excessive heat can lead to the fluid becoming thicker and less effective at lubricating and cooling the transmission components. It is crucial to monitor and maintain the operating temperature of the transmission to prevent fluid degradation.
Contaminants
Despite being sealed, microscopic particles, metal shavings, and other debris can still enter the fluid over time through wear and tear on the components. This contamination can lead to increased friction and wear, further deteriorating the transmission fluid's performance.
Additive Depletion
Transmission fluids are formulated with various additives to enhance their performance, including anti-wear agents, detergents, and anti-oxidants. Over time, these additives can deplete, reducing the fluid's effectiveness in lubricating and protecting the transmission components.
Moisture
Although the system is sealed, moisture can sometimes enter through seals or gaskets, leading to corrosion and negatively affecting the fluid's properties. The presence of moisture can exacerbate other factors, speeding up the degradation process.
Age
Even if the transmission fluid is not in use, it can degrade over time due to chemical reactions. These reactions can change the fluid's viscosity and performance characteristics, making it less effective over time.
Conclusion
Regular maintenance, including periodic fluid changes, is essential to mitigate these issues and prolong the life of the transmission. By understanding the factors that contribute to transmission fluid degradation, you can take proactive steps to maintain your vehicle's transmission system and ensure optimal performance.