The dynamic factor is a common characteristic of vehicle traction and acceleration performance derived from the traction balance of a vehicle. Typically, the dynamic factor is presented as a function of the vehicle theoretical velocity computed using the characteristics of the powertrain only with no tire slippage included. For off-road vehicles requiring large traction in most operational conditions, the tire slippage can impact considerably the vehicle velocity. Furthermore, tire slippages and vehicle actual velocity of multi-wheel drive vehicles significantly depends on the driveline system configuration. In this paper, a new method for analysis of the dynamic factor is proposed which includes the slippages of driving wheels and their influence on the vehicle actual velocity. The method facilitates determination of the effects of terrain grip limitations and slippage on the dynamic factor and acceleration performance of off-road vehicles. An example is given for a 4x4 vehicle, comparing the traditional and proposed approach.