A universal joint (5; 7) comprising: a first fork comprising a first sleeve with a first longitudinal axis (A-A), a first member for connecting to a first shaft, and a first pair of arms diametrically opposite to each other with respect to said first longitudinal axis and extending in a direction opposite the first sleeve; a second fork comprising a second sleeve with a second longitudinal axis, a second member for connecting to a second shaft, and a second pair of arms diametrically opposite to each other with respect to said second longitudinal axis and extending in a direction opposite the second sleeve; a spider comprising: a first pair of trunnions (27.1) coaxial with each other and inserted into a first pair of aligned and opposite seats (61.1) provided in the first pair of arms; and a second pair of trunnions (27.1) coaxial with each other, orthogonal to the first pair of trunnions (27.1), and inserted into a second pair of aligned and opposite seats (61.1) provided in the second pair of arms; wherein a respective needle bearing is provided between each trunnion and the respective seat; wherein: the first sleeve is connected to the first pair of arms through a first collar extending from the first sleeve and having a concave shape and an end edge (91.1), from which the first pair of arms extends; characterized in that: the second sleeve is connected to the second pair of arms through a second collar extending from the second sleeve and having a concave shape and an end edge (91.1), from which the second pair of arms extends; and each collar has an inner concave surface of substantially spherical shape, with a center located on the axis (B-B) of the respective aligned pair of seats (61.1) of the respective pair of arms a first fork comprising a first sleeve with a first longitudinal axis (A-A), a first member for connecting to a first shaft, and a first pair of arms diametrically opposite to each other with respect to said first longitudinal axis and extending in a direction opposite the first sleeve; a second fork comprising a second sleeve with a second longitudinal axis, a second member for connecting to a second shaft, and a second pair of arms diametrically opposite to each other with respect to said second longitudinal axis and extending in a direction opposite the second sleeve; a spider comprising: a first pair of trunnions (27.1) coaxial with each other and inserted into a first pair of aligned and opposite seats (61.1) provided in the first pair of arms; and a second pair of trunnions (27.1) coaxial with each other, orthogonal to the first pair of trunnions (27.1), and inserted into a second pair of aligned and opposite seats (61.1) provided in the second pair of arms; wherein a respective needle bearing is provided between each trunnion and the respective seat; wherein: the first sleeve is connected to the first pair of arms through a first collar extending from the first sleeve and having a concave shape and an end edge (91.1), from which the first pair of arms extends; characterized in that: the second sleeve is connected to the second pair of arms through a second collar extending from the second sleeve and having a concave shape and an end edge (91.1), from which the second pair of arms extends; and each collar has an inner concave surface of substantially spherical shape, with a center located on the axis (B-B) of the respective aligned pair of seats (61.1) of the respective pair of arms