A transmission includes an input shaft, a main shaft, a countershaft, and an oil pump. The input shaft, the main shaft and the countershaft are provided with gearwheels in order to enable torque transfer in a plurality of forward and backward gear speeds. The oil pump is provided with a freewheel mechanism, which includes an oil pump driveshaft, a first pump drive gearwheel and a first and a second freewheel arranged upon the oil pump driveshaft. Both the first and the second freewheel can transfer torque to the oil pump drive shaft in one and the same direction. The first freewheel is in drive connection with the countershaft and the second freewheel is connected to the first pump drive gearwheel, which meshes with a first gearwheel coaxial with the main shaft and which first gearwheel transfers torque in at least one of the forward or backward gear speeds.