In this article, the possibility of steady motion of a tractor-trailer carrying wood, with straight lines regardless of wheel slippage due to the impact dynamics of the non coplanar horizontal surface. In the mathematical model, the authors have built the expressions for evaluation of the wheel's slippage, ability it instability direction of motion when wheels of tractor are slipped, from which to build the conditions for its stabilizing the motion. Research results as a basis to determine the limit speed, some structural parameters and to use rationaly of this equipment.