A method for achieving high quality shifts with one hydraulic unit near
zero displacement when using dog clutches. This method includes selecting
the proper displacement and vocation (whether the hydrostatic unit works
as a pump or motor) of a low displacement hydraulic unit during the
shift, selecting the appropriate speed differential between the clutch
elements, selecting the proper vehicle speed at which to make the shift,
and sequencing the displacement changes of the hydraulic units with a
controller in order to achieve the desired shift conditions.