Besides the planet carrier, the planetary gear system includes the sun gear, ring gear, and what other components?

The correct answer is planet pinions, which are essential components in a planetary gear system. In this system, the planet pinions are the gears that rotate around the sun gear and are engaged with both the sun gear and the ring gear. They are mounted on the planet carrier and allow for the transfer of torque and speed adjustments within the system.

The unique arrangement of the sun gear at the center, the ring gear encircling the planet pinions, and the planet pinions themselves enables the differential motion that is characteristic of planetary gear setups. This design provides high torque output while maintaining a compact size, making it widely used in various machinery, including automotive transmission systems.

In contrast, drive shafts, rings, and gear housings do not serve the same direct role in the functionality of the planetary gear mechanism; instead, they may be part of the overall system but do not directly contribute to the gear ratio changes and motion transfer that define planetary gear systems.