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Transmission fluid, like other mechanical lubricants, is often taken for granted as “just more oil.” However, transmission fluid is very advanced and must perform many roles.



What Is Transmission Fluid?

Transmission fluid is a form of lubricant used to protect internal components of a vehicle’s transmission system in order to avoid premature failure and damage due to friction. There are many types of transmission fluid, and the solution used to protect automatic systems is generally more finely engineered. Synthetic fluids are frequently used in high-performance vehicles, as they can prevent oxidation and more adequately manage friction. At the other end of the spectrum, standard automatic transmission fluid has far fewer additives and is recommended for classic vehicles. Transmission fluid is designed to last for a great deal of time, but it should nevertheless be checked periodically to ensure it is performing its job correctly.

How Does Transmission Fluid Work?

Transmission fluid has many jobs to perform. It’s not just designed to form a film between moving parts, but in certain situations should permit an increased friction level so that clutch materials inside can properly engage. The fluid needs to operate when the internal temperature is extreme and when the vehicle is completely cold, with the level of performance expected to be uniform throughout. In addition to the variable friction modifier, transmission fluid also has anti-wear agents, corrosion and rust inhibitors, performance boosters, foam controllers, and even antioxidants. As transmission manufacturers will often have proprietary components, this fluid is often designed to be manufacturer-specific, as well.

How Is Transmission Fluid Made?

Transmission fluid is a heavily refined product, where the base oil is typically high viscosity and compromises the bulk of the fluid itself. A complex range of additives are mixed in, especially when it comes to automatic transmission systems. Still, some manufacturers recommend that conventional oil is used in their manual transmissions.

What Color is Transmission Fluid Supposed to Be?

Red. Clean transmission fluid is a dark red, translucent color. Transmission fluid is dyed for identification purposes. Over time, the fluid will become darker, causing it to go from its original red to a dark, burnt color due to age and vehicle use. It can also occur when contaminants flow through an improperly functioning transmission filter. Below is a color chart portraying the typical stages your transmission may go through:

When Do I Change My Transmission Fluid?

This answer varies on your car's year, make, and model. You should always consult your owner's manual for the manufacturer's ATF specifications recommended for your vehicle. As automatic transmissions become more complex, there's a need for more technologically advanced fluids to ensure vehicle reliability. Getting the right oil for your car is key to ensuring your transmission operates as designed and you get a smooth driving experience every day.

Why Does Transmission Fluid Fail?

  • Low levels can cause performance degradation and overheating.
  • A buildup of contaminants following extended use can cause the fluid to burn.

What Are the Symptoms of Failure?

  • Difficulty in engaging gear.
  • Slipping transmission.
  • Erratic gear selection.
  • Overheating.

What Are the Implications of Failure?

  • Costly rebuilds.
  • Complete breakdown caused by transmission failure.

Transmission fluid has a very important task to perform, as the components that it protects are complicated and operate in a harsh environment. As a consequence, it’s important to schedule a transmission fluid change in strict accordance with manufacturer recommendations.

If you have questions or concerns about transmission fluid or any of your vehicle’s components or fluids, come into your local Pep Boys where we can answer any question, help you find any part, or perform any vehicle service you might need.