Using methods proposed by Mestel et al. (1988), a large set of low-viscosity numerical models was developed to verify the prediction of these authors that, unless the magnetic field is extremely weak, the influence of the Lorentz force becomes so strong that only very slight differential rotation will be possible. Present results clearly show either the gradual appearance or the maintenance (depending on the initial conditions) of differential rotation over a time of the order of the Alfven time t(A). The conflicting roles of the viscous and magnetic forces are discussed. It is emphasized that uniform rotation can only be achieved with some kind of viscous action; purely magnetic action cannot do the job. 38 refs.