Nonequilibrium simulations of lamellae-forming block copolymers are investigated by means of theoretically informed coarse-grained Brownian dynamics simulations and dissipative particle dynamics. Three lamellar orientations are subjected to steady shear, which differ in the direction of the microstructure with respect to the shear plane. The stable orientations are identified as a function of shear rate. It is found that for Brownian dynamics simulations the transition from parallel to perpendicular does not occur; however, by including local conservation of momentum, the lamellae exhibit this transition. The velocity profiles, stresses, and angles of the blocks in the system were analyzed to yield insights into why parallel orientations are less stable at higher shear rates.