Transmission device for vehicles with a front cab, with front-wheel drive, and with a chassis to which bodywork may be added. This device relates more particularly to vehicles intended, from the outset or after conversion, to take a lowered platform, especially showman's vehicles, mobile laboratories, or travelling sales vehicles. The device, designed for a front-wheel drive motor vehicle with a front cab and a lowered chassis, comprises a front axle assembly and a gearbox, the output shaft of which is arranged longitudinally with respect to the axis of the vehicle, behind the gearbox. It includes a casing, a first gear which can be mounted on the output shaft of the gearbox, a second gear mounted on a transfer shaft towards the front axle assembly and an intermediate gear permanently in mesh with the first gear and the second gear.