hmmm, my beloved 61 savoy , i replaces driverside axel shaft with very bad threads, with a used axel shaft with very good threads, also replaces inner oil seal, bearing  and race,  then put everything back together shim/drums ect ect , tightend down the axel castle nut to specs, then i pulled other side axel shaft out to just replace the inner oil seal, lub the bearing, then put everything  back together shim/drum ect ect and tightend down axel crown nut to specs,      observation, im showing more exsposed threads on one axel shaft than the other,  in other words  one side has more threads showing after the castle nut than the other.  the used axel shaft castle nut, is flush with the the very tip of the end of the threaded shaft, where as the orig axel shaft has maybe 2 or 3 threads exsposed after the casle nut ,   i measured orig and replacement they are the  same    ill check my rock solid never gives me problems 60 savoy, to see if i notice any diff     is this a problem or okay