. Gauging the amount of expansion with a telescoping gage set to the shaft size, which is about .006 inch larger than the cold gear bore diameter. It is this interference fit that holds the gear in place . The gear is starting to turn blue, which means it is about 700 degrees. The thick black goo running down the face of the gear is old grease that has boiled out of casting defects.

Photo by Bill Liebman.