A transmission's final drive (FD) gear is not any one of the speeds. Each of the gears one1 through five has a numerical ratio of how many revolutions of the motor it takes to turn the wheels once. From there, the FD connects the gearbox to the differential. The FD also has a numerical ratio, which means it multiplies the ratio of whatever gear you're in.

If you had two hypothetical transmissions, one with a 4.400 FD and a 4.785 FD but otherwise identical, each of the gears in the 4.785 FD transmission would be effectively shorter because of the higher FD ratio.