A drive unit (1) for a grain elevator, in particular for agricultural machines, has a drive wheel (5) operatively connected to a screw conveyor (3) for conveying crop into the grain elevator. The drive wheel (5) is provided with retainer means (11) which may be engaged in a positive locking and/or friction-type connection with a continuous tension means of the grain elevator provided with one or more paddles so as to drive the continuous tension means. Several openings (13) are provided in the drive wheel (5) between the arms (10) holding the retainer means (11) in such a way that this allowsor facilitates crop conveyed by the screw conveyor (3) into the grain elevator (2) along a direction (F) of conveyance to flow through the drive wheel (5).