pistons that cooperate to form piston areas s 1 a 1 and a 2 and a 3 a and a 3 b the torque section of the tool is shown at 44 along with a hydraulic controller contained in the anti stall tool and shown schematically at 46 the controller includes a pressure control valve 48 a pilot valve 50 a sequence valve 52 and a vent valve 54 a filter for the hydraulic controller is shown at 56 in one embodiment the controller has the three stages of operation 1 active 2 passive and 3 retraction the control valves contained in the controller area of the tool are shown schematically in fig4 pressure lines are shown as solid lines pilot lines are shown as dashed lines and exhaust lines are shown in dotted lines in the following description the pressure ranges are used as examples only they are adjustable to specific motor requirements the active stage applies downward force to the drill bit based on motor back pressure from the positive displacement motor if pressure is less than 400 psi for example the hydraulic pistons apply a downward force which generates more pdm back pressure the vent valve 54 of the controller is open and supplies a pilot signal to the pilot valve 50 if pressure reaches 400 psi the vent valve 54 closes and vents the pilot line for the pilot valve 50 but the detented pilot valve stays in position and the pdm back pressure is sensed by the pressure control valve 48 the pistons apply the downward force until sensed.