text: what does 3:73 racings gears refer to?   gear ratio refers to the difference in the revolution that the engine does with the revolutions that the transmission sends out to the differential. it is commonly refer ed as the supplier first and then the output.  when the output is lower than the input then it is called to be an overdrive.  personally i found it difficult to believe that a racing car has that gear ratio, and more if you refer to third gear if it is very high even for first gear.