Since there's no center differential, what is a part-time 4WD system unable to do?

A part-time 4WD system is designed to be engaged or disengaged by the driver, typically depending on the driving conditions. Unlike full-time 4WD systems that often include a center differential, a part-time system lacks this feature, which is crucial for allowing the front and rear axles to rotate at different speeds. This rotation speed differential is necessary when turning or traversing uneven surfaces, as the wheels on the outside of a turn need to cover more ground than those on the inside.

Without a center differential, when a part-time 4WD system is engaged, both axles are effectively locked together, meaning that they must spin at the same rate. If different wheel speeds are allowed—such as during cornering—there's a risk of drivetrain binding, leading to increased wear and potential damage.

The other options refer to aspects of operation related to power distribution and user controls. For instance, while a part-time 4WD system can provide power to both front and rear wheels, and it can indeed switch between 2WD and 4WD, it does so with the caveat of requiring manual engagement. Additionally, it depends on the driver's input to engage or disengage the 4WD mode, meaning it doesn't automatically adjust