A gear unit (8) for a wind turbine (1) having an input shaft (9) connected to the rotor hub (5) of the wind turbine (1) and an output shaft (10) for connection to an electrical power generator (7), characterized in that the gear unit (8) is provided with a hollow tube (30) which is concentric with the main rotation axis (A-A') and which extends through the gear unit (8) from the input shaft (9) to the output shaft (10), whereby this hollow tube (30) provides a sealing for the gear unit (8) in storage and/or transport.
