Method and control device for operating a drive train

A control unit configured for operating a drive-train of a motor vehicle, the drive train comprising a drive aggregate, a drive output, a group transmission connected between the drive aggregate and the drive output, and a separating cutch connected between the drive aggregate and the group transmission, wherein the group transmission comprises a plurality of sub-transmissions that include (i) at least one main transmission and a splitter group drivingly connected upstream from the main transmission and/or (ii) a range group drivingly connected downstream from the main transmission;

• wherein the control unit is configured to:
• determine that a speed of the motor vehicle is lower than a limit value;
• open the separating clutch;
• pre-select the transmission by changing one of plurality of sub-transmissions to neutral and change at least one other of the plurality of sub-transmissions to a friction-force-locking condition;
• at least partially close the separating clutch after pre-selecting the transmission and bring the drive aggregate to a pre-defined rotation speed;
• determine whether a friction-force-locking group transmission is required;
• check whether a starting shift or a driver-desired shift for the group transmission is called for;
• and
• determine a target rotation speed of the drive aggregate.