A replaceable replacement spindle assembly for both drive (tractor) axles and trailer axles comprises a spindle and seal ring. The spindle is an elongate cylinder having inner and outer bearing surfaces and a threaded portion at one end. The seal ring is a short annular or tubular component having a circular opening sized to achieve an interference fit on a portion of the spindle adjacent the inner bearing surface. The interfering surfaces of the spindle and the seal ring are complementarily dimensioned and tapered so that the surfaces contact when the spindle is properly positioned in the seal ring. Adjacent the end of the spindle opposite the bearing surfaces and threads is an end region with features such as openings or a channel which receive complementary fasteners such as plugs, short bolts or a through bolt.