A large collection of transmission diagrams from various makes and models of car can be found at the Midwest Transmission Center, Inc. website. In addition, transmission diagrams for Fords and Jeeps can be found at the Fordification and Kaiser Willy's websites, respectively.
Midwest Transmission Center, Inc. hosts a large number of transmission diagrams on its site. The company covers manual transmissions from American and foreign-make cars, including Toyotas, Isuzus and Fords.
Although it covers a broad range, if an image from an older model of Ford pickup is needed, the Fordification website provides numerous illustrations and diagrams. It offers a full list of drivetrain diagrams, including transmissions.
Finally, Kaiser Willys' website offers transmission diagrams for T-84, T-90 and T-96 Jeeps.