A motor-vehicle differential comprising a first epicyclic unit, the first epicyclic unit including: - a first sun gear, which is rotatable about a first axis of rotation and is configured for a connection to a first output shaft; - a second sun gear coaxial to the first sun gear, which is rotatable about the first axis of rotation and is configured for a connection to a second output shaft; and - a first planetary unit, which meshes with said first sun gear and said second sun gear, said first planetary unit being carried by a planet carrier, which is rotatable about the first axis of rotation, wherein the differential furthermore includes a second epicyclic unit, the second epicyclic unit including: - a third sun gear coaxial to said first sun gear and said second sun gear; - a ring gear coaxial to said first sun gear and said second sun gear, wherein said ring gear is provided as a casing which houses inside it the first epicyclic unit and the second epicyclic unit, wherein moreover on an outer surface of the casing a toothing is provided that defines a further gear wheel configured to be coupled to an input shaft of the differential; and - a second planetary unit, meshing with said third sun gear and said ring gear, said second planetary unit being carried by the planet carrier of the first planetary unit, the differential being characterized in that it further comprises an engagement device operatively connected to said second epicyclic unit, the engagement device including a first operating condition in which said third sun gear is connected in rotation to said ring gear, and a second operating condition in which rotation of said third sun gear is blocked, the engagement device being configured to connect the third sun gear to a fixed component in the second operating condition. - a first sun gear, which is rotatable about a first axis of rotation and is configured for a connection to a first output shaft; - a second sun gear coaxial to the first sun gear, which is rotatable about the first axis of rotation and is configured for a connection to a second output shaft; and - a first planetary unit, which meshes with said first sun gear and said second sun gear, said first planetary unit being carried by a planet carrier, which is rotatable about the first axis of rotation, wherein the differential furthermore includes a second epicyclic unit, the second epicyclic unit including: - a third sun gear coaxial to said first sun gear and said second sun gear; - a ring gear coaxial to said first sun gear and said second sun gear, wherein said ring gear is provided as a casing which houses inside it the first epicyclic unit and the second epicyclic unit, wherein moreover on an outer surface of the casing a toothing is provided that defines a further gear wheel configured to be coupled to an input shaft of the differential; and - a second planetary unit, meshing with said third sun gear and said ring gear, said second planetary unit being carried by the planet carrier of the first planetary unit, - a third sun gear coaxial to said first sun gear and said second sun gear; - a ring gear coaxial to said first sun gear and said second sun gear, wherein said ring gear is provided as a casing which houses inside it the first epicyclic unit and the second epicyclic unit, wherein moreover on an outer surface of the casing a toothing is provided that defines a further gear wheel configured to be coupled to an input shaft of the differential; and - a second planetary unit, meshing with said third sun gear and said ring gear, said second planetary unit being carried by the planet carrier of the first planetary unit, the differential being characterized in that it further comprises an engagement device operatively connected to said second epicyclic unit, the engagement device including a first operating condition in which said third sun gear is connected in rotation to said ring gear, and a second operating condition in which rotation of said third sun gear is blocked, the engagement device being configured to connect the third sun gear to a fixed component in the second operating condition.