The so-called transfer box is a device that distributes the power of the engine, which can output power to the rear axle or both front and rear axles. From this perspective, it can be seen that the transfer box is actually an accessory on four-wheel drive vehicles. With the development of four-wheel drive technology, the transfer box has been constantly changing and gradually formed a completely different style of transfer box, which is matched with different demands of four-wheel drive vehicles, and their basic principles and functions are also different.

A time-sharing four-wheel drive car is a car that can be a two wheel drive vehicle on off-road conditions and converted to a four-wheel drive vehicle. The time-sharing four-wheel drive transfer box is a purely mechanical device. When the transfer box with this structure is equipped with 4-wheel drive mode, the front and rear axles are rigidly connected, which can achieve a 50:50 distribution of front and rear power, which is very beneficial for improving the vehicle's passability. In addition, due to its pure mechanical structure and high reliability, it is crucial for vehicles that often drive in wilderness areas lacking rescue. Even now, there are still a large number of hardcore off-road vehicles using this transfer box. On the transfer gear lever of this type of vehicle, we will see the shifting gears of 2H, 4H, N, and 4L. When equipped with a 2H, this type of vehicle is a rear wheel drive vehicle, where the power of the engine passes through the gearbox and is directly connected to the rear axle through a transmission shaft. The function of the transfer box is to introduce an output end onto the gearbox and transmit power to the output shaft of the front axle through a silent chain. Of course, this is not a direct connection, otherwise it would be impossible to switch between 4-wheel drive and 2-wheel drive. In fact, it is separated and connected through two sets of gears, and its structure and principle are similar to the first and second shafts of a gearbox. When switching, pull the gear lever of the transfer box to connect and disconnect the power from the front transmission shaft through the fork. Unlike mainstream gearboxes with synchronizers nowadays, there is no synchronizer for switching in this area, as it requires a complete match between speed and wheel speed. This is the basic principle of this transfer box.