The invention relates to a drive device for a change-speed transmission for motor vehicles, having at least one transmission input shaft (14), at least one axially parallel output shaft (18), having a plurality of gearwheel sets which are arranged on the shafts (14, 18) with fixed gearwheels and idler gears which can be switched via synchronizer clutches (38) in order to form forward gears, and having at least one separating clutch (K1, K2). According to the invention, a planetary gear mechanism (40) which can be switched over into two transmission stages is connected upstream of the gearwheel sets of the forward gears (1 to 9), which planetary gear mechanism (40) has a driven input element (42), an output element (50) which outputs to the input shaft (14), and a transmission element (46) which can be braked or coupled in order to switch over the transmission stages, wherein the transmission element (46) can be coupled to an electric machine (54), by means of which the transmission element (46) can be fixed or can be driven in both rotational directions.