It incorporates a body (1) formed in sheet metal by stamping with reduced thickness and maximum inertia, and consists of a modular element ready for mounting which incorporates: a ball joint (2) located inside an external front housing (5) in which it is coupled by means of a lower socket (6) and a cover (7) which fit together and are welded by laser, a front silent-block (3) which reveals a cylindrical body from the surface of which some pairs of securing flaps (11) project radially which are inserted in a slot (8) defined in a concavely curved front housing (9), folded and welded by laser welding, and a rear silent-block (4) which is incorporated in a rear housing (12) by means of some press-fit bushings (15).