In order to investigate the effect of transition of mounted implements from operation to transport on longitudinal stability of a tractor that works on sloping land, a mathematical model was developed. In this model two operation modes for a mounted chisel plow were considered: penetration of the plow into the soil and depth reduction of it, and the effects of transferred forces and torques from the plow on longitudinal stability index of tractor were studied. Longitudinal stability index of tractor was defined as the ratio of the dynamic load of tractor front axle to the static load of it when tractor is on level ground. To test the model, different geometries and mass specifications of tractor MF285 and chisel plow combination were used as the input parameters of the model. According to the results of this study, during plow penetration into the soil, internal forces of the connecting rods were zero and positive values were obtained for the internal force of the connecting rods during depth reduction of the plow; therefore, connecting rods acted only as pulling beams. Furthermore, when the plow depth was increased, the model predicted the increase of the force exerted on the center of gravity of tractor in X direction; however, the force exerted on the center of gravity of tractor in Z direction was almost not affected by the plow depth and height ratio variations. These results were expected and verified that the assumptions of the model have been rational. Moreover, longitudinal stability index of tractor during plow penetration was approximately constant. However at the moment of transition of the plow from operation to transport, this index was reduced abruptly. Therefore in situations that tractor works on steep slopes, plow transition from operation to transport should be avoided
