Which type of 4x4 system remains in two-drive mode until it automatically senses the need for four-wheel-drive traction?

The on-demand 4x4 system is designed to operate primarily in two-wheel drive under normal conditions, which helps improve fuel efficiency. It automatically engages four-wheel drive when it detects a loss of traction, such as when driving on slippery or uneven surfaces. This system provides the driver with the convenience of not having to manually switch between drive modes, as it seamlessly transitions from two-wheel to four-wheel drive only when necessary.

In contrast, the part-time 4x4 system requires the driver to manually engage four-wheel drive when conditions warrant it, and it doesn't operate in four-wheel drive until the driver initiates the change. Full-time 4x4 systems maintain drive to all four wheels at all times, allowing for consistent traction but may not offer the same kind of automatic engagement as the on-demand system. Automatic 4x4 systems, while similar, are often categorized differently than on-demand systems and may employ various modes depending on manufacturer specifications.

Thus, the on-demand system's ability to stay in two-drive mode until traction demands four-wheel-drive makes it unique and efficient for varying driving conditions.