This is a Reverse Idler Gear with 23 teeth for the GM SM465 4 Speed for years 1968 and on. This fits them all! This gear is prone to wear when someone grinds it trying to put it into Reverse too fast. Identify this transmission by the iron or aluminum top cover. It has 2 PTO Openings and has a 12" overall case length. 4 Speed transmission for years 1968 and on.