I put a lot of miles on an "Eaton 15 speed" which is actually a 5 speed main box coupled to a pair of 2-speed rear axles. By putting one axle in low range and the other one in high, an "intermediate" speed is created with the inter-axle differential making up the difference in ratio between the axles. Each gear in the main box is split into 3 ratios by manipulating the electric-shift rear axles with a 3-position switch on the shift knob. There's quite a learning curve involved in making that one shift smoothly.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!