Analysis of advantages and disadvantages of part-time four-wheel drive: powerful off-road, poor in daily life

Part-time four-wheel drive is a tool born for the "wild". It is like a pair of professional equipment for mountain climbing and rock climbing, suitable for conquering rugged mountain roads and muddy valleys. However, if you only commute on asphalt roads every day and occasionally go camping in the suburbs on weekends, not only will it not be used, but it may cause trouble for yourself.

I still remember a friend who bought a hard-core off-road vehicle. He was as excited as a child who had just learned to ride a bicycle. On the first day, he put on the 4H and ran laps in the city. He also said that "four-wheel drive is more stable." As a result, the steering wheel soon became heavy, there was abnormal noise when turning, and the tire edges even wore abnormally. The reason is actually very simple - part-time four-wheel drive does not have a center differential. Once the four-wheel drive mode is engaged, the front and rear driveshafts are mechanically locked at the same speed. During the turning process on paved roads, the front and rear wheels follow different arcs, which inevitably leads to a difference in speed. There is no differential to release it, and it can only be absorbed by tire "slip". It can be serious at best, but can affect control at worst. Especially on rainy days, the risk is even higher.

Therefore, there has been a saying in the industry: "If you can use two-wheel drive, don't use four-wheel drive." Only in non-paved, low-adhesion environments, such as mud, gravel slopes, and snowfields, should you switch to 4H or 4L. 4L is like adding a pair of iron arms to you - it can significantly amplify torque. For example, the transfer case reduction ratio of the Wrangler Rubicon can reach 4:1, which is very powerful when climbing steep slopes or getting out of a stuck car. But what about driving in the city? Fuel consumption keeps rising, and noise, vehicle weight, and comfort all have to be sacrificed.

However, its advantages are undeniable - simple structure, mechanical purity, extremely low failure rate, direct power transmission, and more reliable than most electronic systems in extreme environments. Because of this, many professional off-road vehicles and special vehicles still insist on using purely mechanical part-time four-wheel drive, because in the wild, reliability is life.

However, times have changed, and now there are many tough-looking SUVs, such as the Tank 400, the Tank 500, and the Ford Raptor. They look like off-road warriors, but at their heart are BorgWarner's TOD electronically controlled transfer cases. They silently maintain two-wheel drive to save fuel when commuting in the city, automatically allocate torque when needed, and even lock up to simulate a part-time four-wheel drive effect. They are like urban knights wearing functional suits. They can roam the streets and occasionally go deep into the wilderness.

If mechanical part-time four-wheel drive is the steel tomahawk of the slash-and-burn era, then modern electronically controlled four-wheel drive is the precise Swiss Army knife - different tools have completely different applicable scenarios. The key is, which one do you really need?