A perilously overheated-axle of an over-the-road motor vehicle can be sensed with a novel temperature responsive gauge of the fusible link and spring-loaded button type. When an over-heated-axle melts the gauge fusible link and propels the gauge spring-loaded button toward a plunger surrounded by a tubular fitting for the axle hubcap plug, the plunger is rammed forwardly of the hubcap plug to provide a visually discernible warning that the axle has perilously overheated and requires immediate corrective servicing.
