A gradient viscoplasticity model has been used to analyse stationary and propagative instabilities. It is demonstrated that the use of viscous regularisation is effective for both quasistatic and dynamic problems. Due to the influence of the length scales that are introduced in the model, the numerical simulation gives mesh-objective results with a finite width and unique orientation of the shear band. The numerical simulation of shear banding and propagative Portevin-Le Chatelier bands will be discussed. A 3D analysis of shear banding is shown to give significantly differentresults than the 2D plane strain analysis under similar conditions. Very fine meshes are needed to obtain accurate solutions for the shear band. The Arbitrary Lagrangian Eulerian remeshing method will be used to relocate elements from outside to inside the shear band to minimise computer costs.