Searching for new and cost-effective methods of waste rubber recycling is a subject of research in many scientific centers in the world. In this paper there are presented results of the research of the extrusion process of cheap and environmentally friendly thermoplastic compositions containing 50% wt. of masses of ground tire rubber (GTR). The aim of this study was to determine the relationship between the mixing conditions and properties of obtained products, which is important from a technological point of view. The mixing conditions were determined by using two variables: the screw configuration (co-rotating and counter-rotating) and the type of polyethylene. In the case of both variables, thermoplastic compositions were treated with various shear forces induced by screw speed changes. The influence of mixing conditions on the extrusion process was determined (screw torque, melt flow rate) as well as static and dynamic mechanical properties of obtained materials.