This invention relates to an improved self-threading unit which can be utilized to hold a replacement shock absorber within the cylindrical shroud of a vehicular suspension system commonly referred to as a MacPherson strut suspension assembly. The nut includes a generally cylindrical main body portion having a tapered thread forming portion on the inner wall thereof. The thread forming portion is adapted to roll form buttress-type threads on the upper end of the cylindrical shroud. The upper end of the main body portion includes a top wall having an annular bushing mounted therein for receiving the shock absorber piston rod and centering the nut as it is rotated onto the cylindrical shroud. The top wall is provided with channels extending radially outwardly from the bushing such that, in the event the shock absorber bottoms out, any liquid which may have accumulated on the top wall of the nut, will be evacuated outwardly and will not be forced into the shroud through the bushing.