Abstract: An improved and novel method for controlling the speed of a mechanical apparatus in relation to a reference parameter. The reference parameter can be torque, displacement or similarly measurable parameters. A preferred implementation of the improved and novel method is used for tightening fasteners which utilizes feedback torque to control the speed and sequence of a fastening tool. This feedback torque is constantly monitored to allow continuous adjustment of the speed of the fastening tool and thereby control the torque applied to the fastener. The method is implemented on a fastening tool used to tighten a retainer nut on a pinion gear shaft supported by bearings in a differential housing. The speed of a fastening tool is continuously monitored and changed in response to a rotational torque measurement taken from the pinion gear shaft and bearing assembly.