* Increased Mechanical Stress: Every shift involves engaging and disengaging various components within the transmission – clutches, bands, planetary gears, etc. These components experience wear with each operation. Doing this repeatedly at every stop subjects them to far more stress than normal driving.
* Added Stress on the Shift Mechanism: The transmission's shift mechanism itself (solenoids, valves, etc.) is designed for relatively infrequent shifting. Constant shifting will increase wear and potential failure of these parts.
* Potential for Increased Friction: The act of shifting introduces friction, which generates heat. Excessive heat can damage transmission fluid and internal components.
* Unnecessary Operation: Automatic transmissions are designed to handle stopping and starting efficiently in Drive. Shifting to Neutral doesn't provide any significant benefit in terms of fuel economy or wear reduction in modern vehicles. In fact, it's counterproductive.
While the impact might not be immediately noticeable, consistent shifting to Neutral at every stop would dramatically shorten the lifespan of your automatic transmission compared to normal operation. It's simply not a recommended practice.
