a tone ring assembly for use on a rotatable machine part . the tone ring is able to generate a varying voltage output when rotated at varying speeds . a fixed position magnetic sensor detects this voltage . the tone ring comprises an axially extending main body portion having a plurality of areas able to generate a voltage upon rotation . a retainer having at least one radial flange prevents axial movement of the tone ring and the tone ring includes ribs and spaces on its inside diameter to permit oil to pass therethrough .