Vibration isolators can be dimensioned for securement between a rotational motion source and a rotational motion target. The vibration isolators can include a first end member and a second end member supported in substantially-fixed axial position but axially-rotatable relative to the first end member. An intermediate member can be disposed between and operatively engaging the first and second end members. A rotational motion-to-axial motion conversion system is operatively disposed between the intermediate member and the first end member such that rotation of the intermediate member and the second end member generates axial displacement of the intermediate member relative to the first and second end members. A biasing element can be operatively disposed between the intermediate member and one or more of the first and second end members to bias the intermediate member in an axial direction. Rotary power transmissions or system are also included.
