The Collaborative International Dictionary of English v.0.48:

Axle box \Ax"le box`\
   1. A bushing in the hub of a wheel, through which the axle
      passes.
      [1913 Webster]

   2. The journal box of a rotating axle, especially a railway
      axle.
      [1913 Webster]

   Note: In railway construction, the axle guard, or pedestal,
         with the superincumbent weight, rests on the top of the
         box (usually with a spring intervening), and holds it
         in place by flanges. The box rests upon the journal
         bearing and key, which intervene between the inner top
         of the box and the axle.
         [1913 Webster]