Engineers searched diligently for ways to allow each driving wheel to operate at its own speed. Many ideas were tried with mixed results before the basic design for the present-day, standard differential was finally developed. The successful idea that is still used in principle today was to divide the engine power by dividing the axle in two-attaching each driving wheel separately to its own half-axle and placing in between, an ingenious, free-rotating pinion and gear arrangement. The arrangement was called the differential because it differentiates between the actual speed needs of each wheel and splits the power from the engine into equal driving force to each wheel.
On/off road vehicles and other trucks required to haul heavy loads are sometimes equipped with double reduction axles. A double reduction axle uses two gear sets for greater overall gear reduction and peak torque development. This design is favored for severe-ser-vice applications, such as dump trucks, cement mixers, and other heavy haulers.
The double reduction axle uses a heavy-duty spiral bevel or hypoid pinion and ring gear combination for the first reduction. The second reduction is accomplished with a wide-faced helical spur pin-ion and gear set. The drive pinion and ring gear function just as in a single reduction axle. However, the differential case is not bolted to the ring gear. Instead, the spur pinion is keyed to and driven by the ring gear. The spur pinion is in turn constantly meshed with the helical spur gear to which the differential case is bolted.
Many heavy duty trucks are equipped with two rear drive axles. These tandem axle trucks require a special gear arrangement to deliver power to both the forward and rearward rear driving axles. This gearing must also be capable of allowing for speed differences between the axles.
Two axle hub arrangements are available to provide support between the axle hub and the truck's wheels: the semi-floating type axle and the fully floating type axle. Of the two ,the semi-floating is the simplest, cheapest design to incorporate ,but the fully floating axle is more popular in heavy-duty trucks.
我就这么多分了。老师黑啊。这只是一部分，哪位大哥帮帮忙
所有的车辆都需要承载，重载时，车辆一般会配置双减速桥，双减速桥配置了两套便于大范围齿轮减速和最大扭矩运转的齿轮组。这种设计师用于非常规服务用途的车辆，例如自动倾卸卡车，混凝土搅拌车等其它重型运输车。
双减速车桥采用了重型的螺旋形斜角或准双曲面齿轮和环形齿轮混合装备从而进行第一次减速。第二次减速是伴随着开阔表面的螺旋柱形直齿轮及其它齿轮组的配合完成的。而差速器箱没有被环形齿轮所琐死，相反，环形齿轮能将柱形直齿轮键入并驱动，柱形直齿轮就可以依次不断的与螺旋正齿轮相咬合。
许多重型运输车辆都配备了两个后驱动桥，这种串列车轴的卡车需要一种特殊的齿轮配置方法来解决后驱动桥上的前进与倒车的动力。这些齿轮必须要考虑到车轴间的转速差。
两个车轴轴毂的排列为轴毂和车轮间提供了有力的支持。在半悬挂车抽与全悬挂车轴中，半悬挂车轴是一致设计比较简单的价格便宜的，而全悬挂则多受欢迎于重型卡车中。
