We examine the behaviour of the (310) symmetric tilt boundary with applied shear stress in a face-centred cubic Lennard-Jones crystal. Our purpose is to observe the mechanical properties of grain boundaries resulting from interface melting. The grain boundary is seen to exhibit significant self-diffusion at temperatures above 80% of the bulk melting point . Excess thermodynamic properties and the density of the system change dramatically in this region. However, the system is able to resist shear up to the higher temperature of . Plots of particle trajectories in the interface and estimates of the number of melted layers provide insight into an understanding of this behaviour.