When it became apparent that four speeds weren’t enough, the games began by adding more gears. ZF stepped up to the plate in the early ’90s by launching several new-design five-speeds that involved a lot of stuff. Ford took a simpler approach by turning an A4LD (4R55E) into a 5R55E, mainly by computer strategy cycling the OD section on twice.
Without a significant change in thinking, though, stepping up to six or more speeds would have resulted in a transmission weighing a ton. The answer to the problem was the Lepelletier planetary system.