A hydraulic fluid driven tractor

摘要

A hydraulically driven tractor includes an overpull valve 50 which when actuated displaces from a first position to a second position so as to open a first channel 537 and close a second channel 532 thereby diverting hydraulic fluid from a first flow pathway to a second flow pathway. This causes a change in direction of the tractor. The overpull valve may comprise first and second nested body portions.