A wind turbine system includes turbine blades (16) that turn a low speed shaft (18). A shrink disc coupling (24) radially connects the low speed shaft to a low speed gear box input shaft (22). A brake (26) for the gear box input shaft is operatively connected with the coupling. At least one circuit including a processor controls the brake to keep torsional force on the gear box input shaft below a threshold. The at least one circuit is associated with sensors that can sense conditions away from the gear box input shaft. The at least one circuit can determine when a current condition exists which can cause the threshold to soon be exceeded if preventive braking is not timely applied to the gear box input shaft. The current condition can include a sensed weather condition that is approaching the wind turbine system.