1. A drive control device for a vehicle comprising: an engagement mechanism which includes a revolution component that has plural teeth and is revolved by a torque of an internal combustion engine, and a fixed component that has plural teeth and engages with the revolution component; a torque applying unit which applies a torque to the revolution component; a first transmitting control unit which engages the engagement mechanism to make the engagement mechanism receive a reaction force of the torque of the internal combustion engine, and executes a control for transmitting the torque of the internal combustion engine to wheels; and a torque estimating control unit which executes a control for estimating the torque of the internal combustion engine, wherein the torque estimating control unit comprising: a torque applying control unit which executes a control of the torque applied to the revolution component by the torque applying unit during executing the control by the first transmitting control unit; a phase change detecting unit which detects a phase change between the revolution component and the fixed component in a direction of rotation during executing the control by the torque applying control unit; and a torque estimating unit which estimates the torque of the internal combustion engine based on the phase change detected by the phase change detecting unit and the torque applied by the torque applying unit by the control of the torque applying control unit during executing the control by the first transmitting control unit.