The motor vehicle starter (10) has a casing (18) in which there is arranged an electric motor (12) which rotates a coaxial starter head (22) with the interposing of an epicyclic gearbox (34) including a ring gear (44) made of rigid material (M1) which is housed at least partially in a cavity (58) in the casing and which has an internally toothed cylindrical annular skirt (46) closed at its front axial end by a radially oriented transverse wall (50) with a hole at its centre (52) for the output shaft (42) of the gearbox to pass; the ring gear (44) has pins (P) moulded from a flexible material (M2), notably elastomer material, which are interposed between the ring gear (44) and complementary portions (68) of the cavity (58) of the casing (16, 18) in order to immobilise the ring gear (44) rotationally with respect to the casing (18) and provide a function of torsion damping between these two components (44, 18).