The Synchro-mesh 465 or SM465 is a heavy-duty, four-speed manual transmission built by General Motors for use in light and medium duty trucks from 1968 to 1991 at the factory in Muncie, Indiana; it was designed to replace the somewhat similar Muncie SM420 transmission, which had been in production since just after World War II.
The SM465 can be found in Chevrolet and GMC full-size trucks, Blazers, Suburbans, among other models. Some applications beyond one-ton pickup trucks came with larger input shafts. Favored by off-road drivers, the SM465 has a very low first gear suitable for rock-crawling. The SM465 has developed a reputation as a highly durable transmission. For the 1992 model-year, the SM465 was replaced in 3/4- and 1-ton pickup truck applications by the New Venture Gear 4500 transmission.
The "SM" in the transmission's designation does not stand for Synchro-Mesh, contrary to popular belief. "SM" stands for "SAGINAW MICHIGAN". GM literature also often refer