A gearbox (BV) comprises a secondary shaft (AS) provided with a synchromesh (SB) comprising a flange (FL) comprising a sub-hub (SM) fixedly secured to the secondary shaft (AS) and provided with external splines (CE3), a hub (MO) comprising internal splines (CI1) collaborating with the external splines (CE3) of the sub-hub (SM) to allow translational movement with respect to the latter (SM), and a sleeve (MA) that can undergo a translational movement with respect to the hub (MO) so that the internal splines (CI2) thereof are closely coupled to dogs (CR) of an idling pinion (PF1). This translational movement of the hub (MO) with respect to the sub-hub (SM) guarantees close coupling of the internal splines (CI2) of the sleeve (MA) with the dogs (CR) with a minimal margin for translation, irrespective of dimensional variations in the manufacture of the sleeve (MA) and idling pinion (PF1).

A power train system for a hybrid electric vehicle includes an engine; a first motor operating as a motor for driving the vehicle; a first power transmission mechanism connected between the engine and the first motor; a second power transmission mechanism connected between the first motor and a driving shaft of traveling wheels and transmitting engine power transmitted to the first motor or the engine power and power from the first motor to the driving shaft of the traveling wheels; and a second motor connected to the second power transmission mechanism by a fourth power transmission mechanism to transmit power to the second power transmission mechanism and outputting power for driving the vehicle.

A power train system for a hybrid electric vehicle includes an engine; a first motor operating as a motor for driving the vehicle; a first power transmission mechanism connected between the engine and the first motor; a second power transmission mechanism connected between the first motor and a driving shaft of traveling wheels and transmitting engine power transmitted to the first motor or the engine power and power from the first motor to the driving shaft of the traveling wheels; and a second motor connected to the second power transmission mechanism by a fourth power transmission mechanism to transmit power to the second power transmission mechanism and outputting power for driving the vehicle.

A method of engaging a form-interlocking shifting element to obtain a gear in an automatic transmission in which at least one further, frictional shifting element is involved in obtaining the gear to be engaged and a shifting element, not involved in obtaining the gear to be engaged but which serves as a synchronizing shifting element, is actuated in order to synchronize the interlocking shifting element to be engaged. The further, frictional shifting element, involved in engaging the gear, is engaged and then disengaged, to a defined extent, to bring the frictional shifting element to a slipping condition, in order to ensure the engagement of the interlocking shifting element.

A method of engaging a form-interlocking shifting element to obtain a gear in an automatic transmission in which at least one further, frictional shifting element is involved in obtaining the gear to be engaged and a shifting element, not involved in obtaining the gear to be engaged but which serves as a synchronizing shifting element, is actuated in order to synchronize the interlocking shifting element to be engaged. The further, frictional shifting element, involved in engaging the gear, is engaged and then disengaged, to a defined extent, to bring the frictional shifting element to a slipping condition, in order to ensure the engagement of the interlocking shifting element.