A torque restraint system for a top drive unit in a drilling rig, in which rigid torque arms rotate about a horizontal axis to transmit reactive force from the power swivel to the mast to prevent rotation of the power swivel about a vertical axis. The rotatability of the torque arms also allows lateral displacement of the motor from an operating position to a parked position behind the vertical axis of the well bore. The torque restraint system can be utilized in conjunction with an inclined mast.
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