A starter for a gas turbine engine includes a rotor shaft rotatable about an axis and includes an inner bore extending from an axial end of the rotor shaft with respect to the axis. A sun gear is on the rotor shaft. A lock nut is received against an axial end face of the sun gear and threadedly engaged with an outer diameter of the rotor shaft. A retainer is positioned to bias the nut against the axial end face and includes a projection portion threadedly engaged with the rotor shaft in the inner bore. A bolt through the projection portion is threadedly engaged with the rotor shaft.