Book excerpt: Introduced in 2006, the 6L80 has become the most popular General Motors transmission in production today. Millions are on roads around the world, and the 6L series of transmissions has overtaken the 4L60E as the most popular rebuild in the majority of transmission shops and dealerships today. Automatic transmissions are often seen as mysterious and overly complicated, but much of the guesswork has been simplified to its basic elements in this easy-to-follow guide. This book covers the identification process, operation, diagnostic pointers, common failures, and repair and rebuild procedures for the 6L80 transmission. Upgrades that are available to make the 6L80 more robust are covered as well as the companies that offer upgrades. This detailed, step-by-step instructional manual is authored by engineer, instructor, speaker, and author Steve Garrett. Meticulous step-by-step photos of the rebuild process are featured along with torque specifications and identification of all major and most minor components.