A transmission for a vehicle, comprising: - a first input shaft, a second input shaft, a countershaft, a main shaft, and an output shaft, - a first gear plane comprising a first input shaft gearwheel arranged on the first input shaft, a first main gearwheel rotatably arranged on the main shaft, and a first countershaft gearwheel arranged on the countershaft, the gearwheels of the first gear plane being arranged in mutual driving connection, - a second gear plane comprising a second input shaft gearwheel arranged on the second input shaft, a second main gearwheel rotatably arranged on the main shaft, and a second countershaft gearwheel arranged on the countershaft, the first countershaft gearwheel being selectively drivingly connectable to the second countershaft gearwheel, the gearwheels of the second gear plane being arranged in mutual driving connection, - a first gear engaging device selectively settable to one of: ∘ a neutral state, and ∘ a single engaged state, in which it drivingly connects the first main gearwheel to the main shaft, - a second gear engaging device selectively settable to one of: ∘ a neutral state, and ∘ a single engaged state, in which it drivingly connects the second main gearwheel to the main shaft, wherein the transmission is configured to only enable transfer of torque between the first input shaft and the output shaft via the main shaft, and to only enable transfer of torque between the second input shaft and the output shaft via the main shaft, characterized in that the output shaft is drivingly connectable to the main shaft, and the second gear plane further comprises a first input shaft second gearwheel rotatably arranged on the first input shaft, wherein the transmission further comprises a fourth gear engaging device for selectively rotationally connecting the first input shaft second gearwheel to the first input shaft. - a first input shaft, a second input shaft, a countershaft, a main shaft, and an output shaft, - a first gear plane comprising a first input shaft gearwheel arranged on the first input shaft, a first main gearwheel rotatably arranged on the main shaft, and a first countershaft gearwheel arranged on the countershaft, the gearwheels of the first gear plane being arranged in mutual driving connection, - a second gear plane comprising a second input shaft gearwheel arranged on the second input shaft, a second main gearwheel rotatably arranged on the main shaft, and a second countershaft gearwheel arranged on the countershaft, the first countershaft gearwheel being selectively drivingly connectable to the second countershaft gearwheel, the gearwheels of the second gear plane being arranged in mutual driving connection, - a first gear engaging device selectively settable to one of: ∘ a neutral state, and ∘ a single engaged state, in which it drivingly connects the first main gearwheel to the main shaft, ∘ a neutral state, and ∘ a single engaged state, in which it drivingly connects the first main gearwheel to the main shaft, - a second gear engaging device selectively settable to one of: ∘ a neutral state, and ∘ a single engaged state, in which it drivingly connects the second main gearwheel to the main shaft, wherein the transmission is configured to only enable transfer of torque between the first input shaft and the output shaft via the main shaft, and to only enable transfer of torque between the second input shaft and the output shaft via the main shaft, characterized in that the output shaft is drivingly connectable to the main shaft, and the second gear plane further comprises a first input shaft second gearwheel rotatably arranged on the first input shaft, wherein the transmission further comprises a fourth gear engaging device for selectively rotationally connecting the first input shaft second gearwheel to the first input shaft. ∘ a neutral state, and ∘ a single engaged state, in which it drivingly connects the second main gearwheel to the main shaft, wherein the transmission is configured to only enable transfer of torque between the first input shaft and the output shaft via the main shaft, and to only enable transfer of torque between the second input shaft and the output shaft via the main shaft, characterized in that the output shaft is drivingly connectable to the main shaft, and the second gear plane further comprises a first input shaft second gearwheel rotatably arranged on the first input shaft, wherein the transmission further comprises a fourth gear engaging device for selectively rotationally connecting the first input shaft second gearwheel to the first input shaft.