A transmission unit having a main input which can be connected to a drive source, and a main output which can be connected to the driven wheels, comprises: - a transmission having a first and a second transmission input (5,7) and a transmission output, as well as - a main clutch comprising a first clutch section which is connected to the main input and to the second transmission input, and a second clutch section which is connected to the first transmission input, which transmission: - comprises a first gearing line which comprises a first gear set and a first transmission clutch connected in series to the first gear set, and which has a first input which is connected to the first transmission input, and a first output which is connected to the transmission output, as well as - a second gearing line which runs parallel to the first gearing line and comprises a second gear set and a second transmission clutch connected in series to the second gear set, and which has a second input which is connected to the first transmission input, and a second output which is connected to the transmission output, - a third gearing line which comprises a third gear set and a third transmission clutch connected in series to the third gear set, and which has a third input which is connected to the second transmission input, and a third output which is connected to the transmission output, where the second transmission input can be connected via a short-circuit clutch to the second gearing line in between the second transmission clutch and the second gear set, characterized in that the transmission comprises a fourth gearing line which comprises a fourth gear set and a fourth transmission clutch connected in series to the fourth gear set, and which has a fourth input which is connected to the first transmission input, and a fourth output which is connected to the transmission output. - a transmission having a first and a second transmission input (5,7) and a transmission output, as well as - a main clutch comprising a first clutch section which is connected to the main input and to the second transmission input, and a second clutch section which is connected to the first transmission input, - comprises a first gearing line which comprises a first gear set and a first transmission clutch connected in series to the first gear set, and which has a first input which is connected to the first transmission input, and a first output which is connected to the transmission output, as well as - a second gearing line which runs parallel to the first gearing line and comprises a second gear set and a second transmission clutch connected in series to the second gear set, and which has a second input which is connected to the first transmission input, and a second output which is connected to the transmission output, - a third gearing line which comprises a third gear set and a third transmission clutch connected in series to the third gear set, and which has a third input which is connected to the second transmission input, and a third output which is connected to the transmission output, where the second transmission input can be connected via a short-circuit clutch to the second gearing line in between the second transmission clutch and the second gear set,