Wear in swashplate type axial piston pumps mainly occurs in three tribological contact pairs. These are swashplate-slipper, piston-cylinder and cylinderblock-valveplate. This article focuses on a simulation model, based on the approach of Archard and Fleischer, to predict the wear in the pistoncylinder contact. Besides general geometric data, the exact piston and cylinder contours and the wear-induced material removal over time are taken into account. A special focus in the simulation is on the investigation of the dependency of the viscosity of the hydraulic fluid on the wear. First results from test runs demonstrate a good correspondence between the simulation and measured wear on a test bench.