What is the source of the differential action of the differential gear device of the stacker?

The differential gear device in a stacker is primarily influenced by the wheels. The differential function allows the wheels on either side of the truck to rotate at different speeds, which is essential for maintaining stability and control during turns. When a forklift or stacker turns, the wheel on the outside travels a longer distance compared to the wheel on the inside. The differential mechanism helps to accommodate this difference in speed between the wheels, enabling smooth and efficient maneuvering without putting excessive strain on the driveline or the tires.

This functionality is crucial in warehouse or industrial settings where stackers often navigate narrow aisles and tight corners, providing better handling and safety during operation. Therefore, the correct answer identifies the wheels as the source of the differential action, highlighting the importance of their role in effective vehicle maneuverability.