The AOD transmission, a mainstay of Ford's engineering development, was created to improve fuel efficiency in American automobiles by replacing outdated 3-speed automatics. It has four forward speeds, including a useful overdrive gear that reduces RPMs when cruising on the highway, and is constructed with a lightweight aluminum case. The AOD is favored by enthusiasts due to its robust compatibility with V8 engines, ease of operation, and upgradeability with shift kits. The AOD is an intelligent, tried-and-true option for modern performance with vintage dependability, whether you're repairing a Fox-body Mustang or upgrading a vintage Ford pickup.