A mechanical assembly controls the position of a trencher attached to a tractor and includes a positioning arm attached to the tractor at one end and the trencher at an opposite end. The positioning arm levers the trencher about a single fulcrum point on the positioning arm. A first lift cylinder has a base end connected to the tractor and an extendible end connected to the first positioning arm at the single fulcrum point. The positioning arm pivots about the tractor to move the trencher in response to the lift cylinder. Grade control cylinders are also attached to the positioning arm and the trencher to control the angular position of the trencher in relation to the ground below.