If the front and rear axles are connected to the frame in SINOTENG loaders, four points of the SINOTENG loader will be contacted with the ground during the running process; when the SINOTENG loader runs on the uneven ground, the fourth wheel will be suspended not to have the function of supporting the whole SINOTENG loader because three points (wheels) can determine a plane; at the same time, because the three wheels bear excessive loads, all parts will be easily damaged. So through the under-frame or the swing frame of SINOTENG loaders, the rear axle and the frame are in the non-rigid connecting state, and can swing in the running process, so that two wheels of the rear axle can contact the ground simultaneously no matter whether the ground is flat.
