Why would 4 wheel drive quit working?

Four-wheel drive (4WD) can quit working due to several reasons, including a malfunctioning transfer case, damaged driveshaft, or issues with the front or rear differentials. Electrical problems, such as a blown fuse or faulty wiring, can also prevent 4WD engagement. Additionally, low fluid levels or contamination in the transfer case or differentials can impair functionality. Regular maintenance is essential to prevent these issues.