A torque-coupling device for coupling driving and driven shafts. The torque- coupling device includes a casing having a locking surface, a torque converter, and a locking piston having an engagement surface axially moveable to and from the locking surface of the casing. The locking piston includes a vibration damper including a torque input member and a unitary radially elastic output member elastically coupled to the torque input member. The torque input member includes a radially oriented first retainer plate and at least one supporting member mounted thereto. The output member includes an output hub and at least one elastic blade configured to elastically engage the supporting member upon rotation of the first retainer plate with respect to the output member. The torque input member of the vibration damper non-rotatably engages the turbine wheel and is axially moveable relative to both the impeller wheel and turbine wheel.