Back in the late 1970s I drove a Freightliner with a 270 cat and a 15 speed Eaton over those same roads- - - - -"slow" and "slower" was the order of the day. That drivetrain was a straight 5 speed transmission with a 3 speed rear axle setup. "Intermediate" axle ratio was one electric shift 2 speed in low, and the other in high, with the power divider taking up the difference.
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!