What is the proper method for checking the automatic transmission fluid?

The proper method for checking the automatic transmission fluid involves both hot and cold checks. This approach is essential because the viscosity of the transmission fluid changes with temperature. A cold check provides an initial indication of fluid level when the transmission is at ambient temperature, while a hot check, done after the vehicle has been run, gives a more accurate reading when the fluid has expanded in response to heat.

During the hot check, the transmission should be in the "Park" position, and the engine should be running. This allows you to measure the fluid level under the conditions it typically operates. Each vehicle may have specific guidelines, such as the ideal temperature range for the fluid when it is checked, to ensure accuracy.

Choosing only one method, such as relying solely on a cold check, can lead to an inaccurate assessment that may overlook potential issues like fluid starvation or overfill. Therefore, employing both methods gives a comprehensive understanding of the transmission fluid condition, ensuring optimal performance and avoiding potential damage to the transmission system.