What is the difference between part-time four-wheel drive and on-demand four-wheel drive?

[LaIsla]

On-demand four-wheel drive generally operates in two-wheel drive mode and automatically switches to four-wheel drive when necessary; the part-time four-wheel drive system requires manual switching between two-wheel drive, high-speed four-wheel drive, and low-speed four-wheel drive modes. Below are the specific differences between the two: 1. Different vehicle applications (1) Part-time four-wheel drive typically refers to four-wheel-drive vehicles with a manual transfer case. Most older domestic SUVs and the Jeep Wrangler use this system. These vehicles are usually equipped with solid front and rear axles, manual operation, simple structure, high reliability, and facilitate the installation of rear differential locks or front hub locks. (2) On-demand four-wheel drive is adopted by most urban SUVs. Among various four-wheel-drive systems, it achieves a balance between operational convenience and cost. They are mostly front-transverse engine configurations, with a drive shaft leading to the rear axle. Power is transmitted through a multi-plate clutch in series with the rear differential. Normally, it operates in front-wheel drive, and the computer automatically engages the clutch to drive the rear wheels when wheel slippage is detected. 2. Different technologies (1) Part-time four-wheel drive: The driver manually selects between two-wheel drive or four-wheel drive modes by engaging or disengaging the transfer case. This is the most common drive mode in SUV models. Its advantage is that it ensures both the vehicle's power and off-road capability while maintaining fuel economy. The slight drawback is that the driver needs to judge road conditions and manually operate the drive mode. (2) On-demand four-wheel drive: The switching between two-wheel drive and four-wheel drive is controlled by a computer chip. The notable feature of this system is that it inherits the advantages of full-time four-wheel drive and part-time four-wheel drive while compensating for their shortcomings. It can automatically identify the driving environment and control the switching between two-wheel drive and four-wheel drive modes based on changes in driving conditions. On low-traction surfaces such as bumpy, hilly, or winding roads, the vehicle automatically sets to four-wheel drive mode, while on flatter urban roads, it switches to two-wheel drive.