How do you check the level of transmission fluid?

The correct method to check the level of transmission fluid is to do so with the engine running and to remove the dipstick to check the fluid level. This is crucial because transmission fluid expands as it warms up, and checking it while the engine is running gives a more accurate reading of the fluid level at operating temperature.

When the engine is running, the transmission pump circulates the fluid, ensuring that it fully fills the transmission and any associated housings. This allows for a proper measurement of the fluid level when the dipstick is inserted back into the tube and removed for inspection.

Measuring fluid level with the engine off can lead to an incorrect assessment, as the fluid may settle and not reflect the true level needed for optimal transmission function. Furthermore, simply checking warning lights does not provide a direct measure of fluid level or condition, and listening for fluid noises when the car is in gear does not offer a reliable method of checking fluid levels. These practices do not allow for an accurate evaluation of the transmission fluid, making the procedure with the engine running the most appropriate and effective method.