1. A computer-implemented method of simulating a drive-train system, the method being performed using one or more processing units, the method comprising: developing a drive-train simulation model having a mathematical drive-train equation, the drive-train simulation model being represented in a tree-type typology; trimming the mathematical drive-train equation to a steady-state condition; and executing a time domain simulation of the drive-train system with the one or more processing units using a recursive algorithm, the recursive algorithm comprising: first, performing an outward kinematics recursion; second, performing an inward dynamics recursion to compute a rotational inertia quantity and a torque quantity; and finally, performing an outward acceleration recursion; wherein the outward acceleration recursion is based upon the rotational inertia quantity and the torque quantity.