A power driver may include a housing, a tool chuck and a power take off mechanism. The tool chuck may have an input shaft mounted for rotation on the housing. The input shaft may support chuck jaws. A chuck actuating shaft may be mounted for rotation on the input shaft. The power take off mechanism may be connected to the tool chuck. The power take off mechanism may be adjustable into a DRILL/DRIVE MODE to rotationally drive the input shaft and the chuck actuating shaft together as a unit. Here, a brake may resist relative rotation between the input shaft and the chuck actuating shaft. The power take off mechanism may be adjustable into a CHUCK MODE in which a gear mounted on the input shaft may rotationally drive the chuck actuating shaft relative to the input shaft. Here, the brake may be deactivated.