Abstract: A method for operating a drive train of a motor vehicle, where the drive train includes a drive aggregate, a group transmission connected between the drive aggregate and a drive output, and a separating cutch connected between the drive aggregate and the group transmission. If a speed is lower than a limit value, the separating clutch is opened and for transmission preselection one or all the other sub-transmission(s) is/are changed to a friction-force-locking condition. The separating clutch is then at least partially closed and the drive aggregate is brought to a defined rotation speed. When a friction-force-locking group transmission is required, it is checked whether a starting gearshift or a driver-desired shift for the group transmission is called for and the target rotation speed of the drive aggregate is checked. Depending on the results, the sub-transmission can be synchronized by a transmission brake or by the drive aggregate.

Abstract: A method for operating a motor vehicle drive train having a drive aggregate, an automated group transmission connected between the drive aggregate and a drive output, and a disconnect clutch connected between the drive aggregate and the group transmission. The group transmission has a plurality of sub-transmissions, including a main transmission, a splitter group upstream from the main transmission, and a range group downstream from the main transmission. When the disconnect clutch cannot be shifted to carry out a shifting operation in the group transmission, an emergency shifting program is activated. Shifting from a current gear to a target gear is carried out automatically, as a function of input rotation speed of the group transmission or as a function of rotation speed of the drive aggregate, while the disconnect clutch is closed and where the main transmission and/or the range group participate exclusively, but not the splitter group.

Abstract: A method for operating a drive train of a motor vehicle, where the drive train includes a drive aggregate, a group transmission connected between the drive aggregate and a drive output, and a separating cutch connected between the drive aggregate and the group transmission. If a speed is lower than a limit value, the separating clutch is opened and for transmission preselection one or all the other sub-transmission(s) is/are changed to a friction-force-locking condition. The separating clutch is then at least partially closed and the drive aggregate is brought to a defined rotation speed. When a friction-force-locking group transmission is required, it is checked whether a starting gearshift or a driver-desired shift for the group transmission is called for and the target rotation speed of the drive aggregate is checked. Depending on the results, the sub-transmission can be synchronized by a transmission brake or by the drive aggregate.