a tensioner for a power transmission system includes two tensioning arms operatively engaged with the strand of the chain or the belt of the power transmission system . the upper end of each tensioning arm is connected to a two way damper which is pivotally mounted between the upper ends of the tensioning arms . when a pre - determined chain tension overload threshold is reached , the amount of torque required to overcome the coefficient of friction the damper allows the tensioner to adjust the tension in the chain with minimal oscillations and minimal phase change variation .