Mud Motor consists of a power section and a bearing section.

The bearing section is assembled with the following to impart a bend to a motor:
• Adjustable bent housing assembly — for DRU motors. The adjustable bent housing assembly allows rig floor bend adjustment.
• Bent sub — for DOT motors. The motor bend is adjusted by changing the bent sub. For a straight motor, a straight sub is used instead of a bent sub.

The hydraulic downhole motor is a volumetric (hydrostatic) machine. Torque output and rotary speed depend on the number of rotor and stator lobes (lobe configuration). The more lobes, the lower the speed and the higher the torque. Speed, torque output, power, differential pressure are proportional to the flow rate of the drilling fluid. The longer the motor with respectively more stages, the higher the horse power and torque output of the motor.

The power section converts the hydraulic energy of the drilling fluid into mechanical rotary energy. The power section is composed of a rotor and a stator. The stator is a steel tube with left-hand lobe elastomer molded to the interior surface of the tube. The elastomer is formed with left-handed helical lobe profile. The steel rotor has external lobes, one fewer than the stator. As the drilling fluid is pumped through by mud pumps from the surface, it causes the rotor to rotate inside the stator.
The bearing section supports the hydraulic thrust of the power section, bottom reaction and radial loads from the bit during drilling. The bearing section includes radial thrust ball bearing or multiple-row rubber/metal thrust bearing and radial journal bearings