A drive unit includes an electric motor, a worm shaft coupled to the motor, a worm gear engaging with the worm shaft, and an output shaft connected to the worm gear. The motor has a motor shaft on which the worm shaft is fixed. The worm shaft is made of plastic. The drive unit further includes a metallic sleeve press fitted to the motor shaft. An outer profile of the sleeve is non-circular. A correspondingly shaped receiving hole is formed in the worm shaft to receive the sleeve. The sleeve rotates with the motor shaft and drives the worm shaft.