The invention discloses systems for improving performance and operational efficiency of wireline tractors. A cooling system improves power capabilities of electrical motors mounted in wheels, which are mounted on a linkage pivotably connected to an arm extended from a tractor tool body, in an in-line arm configuration. The linkage and arm mechanism significantly improve the tractor's ability to traverse wellbore obstructions. The hydraulic system of the tractor ensures adequate wellbore centralization.