Lepelletier planetary system Archives - Transmission Digest
Lepelletier Planetary System

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.