There was also an over/under auxiliary transmission made by Brown/Lipe ("Brownie") which was used in conjunction with the main transmission. It allowed a driver to have an underdrive/direct/overdrive selection for each main transmission ratio. A 4-speed became a 12-speed setup with the Brownie transmission in the mix. I learned to drive big rigs on a B-73 Mack with a Tri-plex transmission- - -two shifters and a 5X3 speed setup in the same transmission housing. Once I got it rolling, all the shifts were done without using the clutch.
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!