Abstract: A pumping unit comprising a supporting post and a walking beam, having a head end and a tail end, pivotally connected to the post to allow for rocking of the beam about a horizontal pivot axis. The head end is connected to a vertical pump rod. The walking beam is also connected to one end of an arm, the opposite end of which is connected to a drive assembly for rocking of the beam about the horizontal pivot axis to reciprocate and produce a predetermined number of up and down strokes per minute of the pump rod. The drive assembly includes a rotating power device connected by sheaves and belts a transmission assembly whereby rotation of the power device is translated to a longitudinal force on the arm for rocking of the beam. The drive assembly is further characterized by a speed reducer interpositionable between the power device and the power transmission assembly to substantially reduce the number of up and down strokes per minute of the pump rod.