Part-Time Four-Wheel Drive (4WD) is a drivetrain system that allows a vehicle to switch between two-wheel drive (2WD) and four-wheel drive. In 2WD mode, power is sent to only one set of wheels, usually the rear, which is more fuel-efficient for regular driving conditions. When traction is needed, the driver can engage 4WD, distributing power to all four wheels for improved grip on slippery or uneven surfaces. This system is commonly found in SUVs and trucks, making them suitable for off-road adventures or challenging weather conditions. Part-Time 4WD typically requires the driver to manually shift between modes, providing flexibility based on driving needs.