JS-400A/404A tractor is a kind of medium size wheeled tractor, which are equipped with reinforced front and rear axles, adjustale wheel base, compound transmission box with more speeds, double acting clutch and bigger torque reserve. In a word, they have many advantages such as perfect hydraulic suspension system, reliable air brake device to meet with working requirements, retional construction, good performance, larger horsepower, lower oil consumption, easy maintenance etc.