Filtration device of swinging oscillator type, in particular for a motor vehicle transmission, having an axis of rotation and comprising: - at least one support element able to be rotated about the axis of rotation, - at least one mass able to oscillate, with respect to the said support element, in an oscillation plane orthogonal to the axis of rotation, - means for guiding the mass with respect to the support element, acting between the said at least one support element and the said at least one mass, and - end-of-travel stop means able to limit, during operation, the oscillations of the said at least one mass with respect to the said at least one support element, the filtration device comprising damping means which are able to selectively produce a friction damping effect to dissipate by mechanical friction at least part of the energy of the said at least one mass, characterized in that the said damping means comprise at least one elastically deformable member which is able to respectively occupy at least one standby state and a compressed state and in that, when the said at least one mass oscillates circumferentially beyond a defined angular position, the said at least one elastically deformable member is compressed, between a first position and a second position, along a compression travel in the course of which the said member dissipates energy by mechanical friction so as to produce the said friction damping effect on the said at least one mass and in that, oscillating beyond a defined position, the said at least one mass compresses the said at least one elastically deformable member along a compression travel which is perpendicular to the oscillation plane of the said at least one mass. - at least one support element able to be rotated about the axis of rotation, - at least one mass able to oscillate, with respect to the said support element, in an oscillation plane orthogonal to the axis of rotation, - means for guiding the mass with respect to the support element, acting between the said at least one support element and the said at least one mass, and - end-of-travel stop means able to limit, during operation, the oscillations of the said at least one mass with respect to the said at least one support element, the filtration device comprising damping means which are able to selectively produce a friction damping effect to dissipate by mechanical friction at least part of the energy of the said at least one mass, characterized in that the said damping means comprise at least one elastically deformable member which is able to respectively occupy at least one standby state and a compressed state and in that, when the said at least one mass oscillates circumferentially beyond a defined angular position, the said at least one elastically deformable member is compressed, between a first position and a second position, along a compression travel in the course of which the said member dissipates energy by mechanical friction so as to produce the said friction damping effect on the said at least one mass and in that, oscillating beyond a defined position, the said at least one mass compresses the said at least one elastically deformable member along a compression travel which is perpendicular to the oscillation plane of the said at least one mass.