Differential group for a heavy vehicle, said differential group comprising a casing defining a space, a differential and a transmission housed inside said space, said differential being configured to divide an input torque from a drive source to said differential group to a torque of axle shafts (4, 5) of said vehicle coaxial around an axis, said transmission being operatively interposed between said driving source and said differential and comprising a rotating structure carried rotationally free from said casing and a planetary, said rotating structure being operatively interposed between said driving source and said planetary and defining a space housing said planetary and said differential, said planetary comprising: a solar rotationally carried around one of the axle shafts (4, 5) and defining a toothing, a crown rigidly carried by said rotating structure and defining a toothing, and a plurality of satellites meshing with said toothing (29, 31) of said solar and said crown and configured to rotate around a pin rigidly carried by a carrier of said differential, said differential group comprising actuator means (41, 60, 70) configured to control said solar so that it assumes a first operating condition in which it is rotationally coupled to said rotating structure or a second operating condition in the which is rotationally coupled to said casing, characterized in that said solar comprises a sleeve operated by said actuator means to move along said axis and positioned around one of the axle shafts (4, 5), said sleeve also defining a first toothing and a second toothing configured respectively to mesh alternately with respective teeth (39, 38) carried by each pin of said satellites and by said carcass as a function of the position of said sleeve on said axis. said differential being configured to divide an input torque from a drive source to said differential group to a torque of axle shafts (4, 5) of said vehicle coaxial around an axis, said transmission being operatively interposed between said driving source and said differential and comprising a rotating structure carried rotationally free from said casing and a planetary, said rotating structure being operatively interposed between said driving source and said planetary and defining a space housing said planetary and said differential, said planetary comprising: a solar rotationally carried around one of the axle shafts (4, 5) and defining a toothing, a crown rigidly carried by said rotating structure and defining a toothing, and a plurality of satellites meshing with said toothing (29, 31) of said solar and said crown and configured to rotate around a pin rigidly carried by a carrier of said differential, said differential group comprising actuator means (41, 60, 70) configured to control said solar so that it assumes a first operating condition in which it is rotationally coupled to said rotating structure or a second operating condition in the which is rotationally coupled to said casing, characterized in that said solar comprises a sleeve operated by said actuator means to move along said axis and positioned around one of the axle shafts (4, 5), said sleeve also defining a first toothing and a second toothing configured respectively to mesh alternately with respective teeth (39, 38) carried by each pin of said satellites and by said carcass as a function of the position of said sleeve on said axis. a solar rotationally carried around one of the axle shafts (4, 5) and defining a toothing, a crown rigidly carried by said rotating structure and defining a toothing, and a plurality of satellites meshing with said toothing (29, 31) of said solar and said crown and configured to rotate around a pin rigidly carried by a carrier of said differential, said differential group comprising actuator means (41, 60, 70) configured to control said solar so that it assumes a first operating condition in which it is rotationally coupled to said rotating structure or a second operating condition in the which is rotationally coupled to said casing, characterized in that said solar comprises a sleeve operated by said actuator means to move along said axis and positioned around one of the axle shafts (4, 5), said sleeve also defining a first toothing and a second toothing configured respectively to mesh alternately with respective teeth (39, 38) carried by each pin of said satellites and by said carcass as a function of the position of said sleeve on said axis.