6L80 transmission is the newest addition to GM’s line of heavy-duty transmissions. The 6L80 transmission is a heavy-duty automatic transmission that was introduced in the 2004 model year. It is used for light truck and SUV applications. The gear ratios are 3.06, 2.34, 1.67, 1.00, and 0.75:1 with overdrive off or 0.87:1 with overdrive on (2nd-6th gears).
The 6L80 transmission has six forward gears and one reverse gear with an overdrive gear that can be engaged as an option for improved fuel economy in certain conditions (mostly highway driving). The GM 6L80 transmission is the first-ever six-speed fully electronic automatic transmission for on-highway commercial trucks and buses. It offers a number of advantages over previous generation transmissions, including increased fuel efficiency and improved engine performance.