A gearing unit with planetary gearing employs a load sensor in the form of a stationary pin provided with a strain gauge transducer easily accessible via a bore in its casing. A brake with respective plate carriers is associated with the planetary gearing. One of these carriers is held stationary with the aid of the load sensor while the other of the carriers meshes via teeth with a rotatable component of the gearing. During operation the carriers lock together to hold the component of the planetary gearing stationary to permit drive to be transmitted. The load sensor is then subjected to force proportional to the dynamic loading on the gearing and brake. In the event of overloading the carriers are disengaged by hydraulic force in response to a signal from the sensor to permit the planetary gearing component to rotate and thus interrupts the drive.