METHOD FOR AUTOMATICALLY CONTROLLING THE GEAR RATIO OF A TRANSMISSION OF A VEHICLE, CONTROL SYSTEM, VEHICLE AND COMPUTER PROGRAM FOR CARRYING OUT SUCH METHOD

The method according to the invention, for automatically controlling the gear ratio of a transmission (1, 1') of a vehicle such as a wheel loader, comprises the step of determining the disturbance torque fraction (T_ext) of the load torque applied to the first input shaft (3) at a predetermined instant (i) on the basis of the rotational speed (n_eng) of the first input shaft (3) and of one or more of the following quantities: A) the torque (T_eng) applied to the engine shaft or to the first input shaft (3) by the primary engine (29); B) the torque (T_c) applied at least to the first output shaft (19); C) the rotational inertia of the primary engine (J_eng) reduced to the first input shaft (3); D) the rotational inertia (J_htv) of the transmission (1) reduced to the first input shaft (3).