1. Absorbing foreign advanced technology of tractor drive axle; 2. Adopting middle-positioned drive axle and swinging central balance pin; 3. The internal structure including central speed reducer ,differential ,terminal double bevel gear reducer ,etc; 4. The central transmission system is compact and occupies little space ,which enhances the tractor 's passing capacity; 5. Adopting front-positioned type mid-position cylinder ,which is reliable for steering ,looks beautiful and novel; 6. Terminal and king pin streering system adopts composite material sliding bearing structure ,which makes the streering light and flexible; 7. High ground clearance can improve the passing capacity of tractor; 8. Adaptive for 16-28PS narrow-track four-wheel drivetractor.