The Collaborative International Dictionary of English v.0.48:

Driving \Driv"ing\, a.
   1. Having great force of impulse; as, a driving wind or
      storm.
      [1913 Webster]

   2. Communicating force; impelling; as, a driving shaft.
      [1913 Webster]

   Driving axle, the axle of a driving wheel, as in a
      locomotive.

   Driving box (Locomotive), the journal box of a driving
      axle. See Illust. of Locomotive.

   Driving note (Mus.), a syncopated note; a tone begun on a
      weak part of a measure and held through the next accented
      part, thus anticipating the accent and driving it through.


   Driving spring, a spring fixed upon the box of the driving
      axle of a locomotive engine to support the weight and
      deaden shocks. [Eng.] --Weale.

   Driving wheel (Mach.), a wheel that communicates motion;
      one of the large wheels of a locomotive to which the
      connecting rods of the engine are attached; -- called
      also, simply, driver. See Illust. of Locomotive.
      [1913 Webster]

WordNet (r) 3.0 (2006):

driving axle
    n 1: the axle of a self-propelled vehicle that provides the
         driving power [syn: live axle, driving axle]