An apparatus for producing a preload in a differential mechanism includes a housing formed with a first screw thread, a component located in the housing and for supported in revolution about a first axis on the housing by a bearing. A nut includes a second screw thread engaged with the first screw thread, recesses distributed about the first axis, and a preloaded surface that contacts the bearing with a force produced by applying torque tending to engage the first and second screw threads. A lock tab, secured against rotation relative to the nut, includes a surface that overlaps at least one of the recesses and by which the lock tab is secured to the nut.