In the last years the engine-transmission system was optimized substantially with the purpose to obtain advanced dynamic performances. The transmission must cooperate with the propulsion system in a perfect way to obtain maximum acceleration performances and a low fuel consumption. This paper presents an extensive study of the acceleration performances of an automobile equipped with a mechanical transmission, the study is accomplished through numerical simulation. The numerical simulations were made with the Matlab-Simulink program. The article analyses the dynamic behaviour of an elastic mechanical transmission. The obtained results are similar with the results given by the constructor. The conclusion of the study is that the simulation model presented in this paper can be successfully used for all the automobiles equipped with a mechanical transmission for a fast analyse of the acceleration performances, as well can be used to optimize these performances.