Drive line operation method

A method of operating a drive train of a vehicle in which the drive train comprises a drive unit, a transmission, and an all-wheel splitter having an automatically operated clutch, the all-wheel splitter being positioned between the transmission and an output, whereby the clutch of the all-wheel splitter being operated in such way that the all-wheel splitter splits a transmission output torque in the sense of a variable torque distribution for driven axles of the output, whereby the splitting of the transmission output torque for the driven axles being set by a control unit, implemented in an all-wheel drive strategy in such a way that the transmission output torque, less a nominal torque which being set by the all-wheel drive strategy, being transferred to a first driven axle, and the nominal torque being transferred to a second driven axle, the method comprising the steps of:

• activating a clutch monitoring function if defined operating conditions of the drive train are met,
• replacing the nominal torque, set by the all-wheel strategy, by a default torque of the clutch monitoring function in such a way that the torque, which being transferred to the second axle by the clutch, is first increased, then maintained constant, and then reduced again, whereby at least after the increasing of the torque being transferred from the clutch to the second drive axle, and after the reducing of the torque being transferred by the clutch to the second driven axle,
• calculating a change of a differential rotational speed value, between the driven axles and assigned clutch elements, and if at least one of the calculated changes is higher than a defined limit, assuming that the clutch is operating properly, and
• when all calculated changes in the differential rotational speed value are lower than the defined limit value, assuming that the clutch is not working properly.