What does O/D mean in an automatic transmission?

[LeJulia]

The O/D switch (overdrive) on the gearshift refers to overdrive transmission, which is commonly found in non-manual-automatic transmissions. Here is an introduction to the O/D button: 1. Automatic transmission O/D: O/D is the abbreviation for OVERDRIVE, meaning overdrive transmission, typically used in non-manual-automatic transmission models, especially common in Japanese cars. This button is generally not used in daily driving. Taking a 4-speed automatic transmission as an example, when the transmission gear ratio is less than 1 during operation, this gear is called OVERDRIVE. For instance, when the 4th gear ratio is 0.697, it means the engine turns one revolution while the transmission turns only 0.697 revolutions. This allows the engine to increase the car's speed without requiring high RPMs, thereby improving fuel economy and reducing wear on internal engine components, extending the engine's lifespan. 2. Location and function: Typically, this button is designed on the side of the gearshift lever, while some models place it on the center console. When driving at high speeds or needing to overtake, activating the O/D gear can reduce engine load, eliminating the need for high RPM operation and lowering fuel consumption. In congested traffic, pressing the O/D button prevents the transmission from shifting to the 4th gear and reduces unnecessary switching of the shift solenoid valve.