The invention concerns a device for lubricating gears (1) idly rotating about a gearbox shaft (3) comprising an axial conduit (9) of said shaft connected to at least one radial lubricating bore (11) emerging towards the bearing zone (7) and a synchronizing unit (2) of an idler, and a fixed lubricating tube (12) extending inside the conduit (9). The invention is characterized in that the tube (12) has lubricating holes (16) facing the bores (11) of the shaft with sufficient spacing for the oil accumulated between the tube (12) and the shaft (3) to be continuously sucked towards bearing zones (7) and synchronizing units (2) of the gears (1).
