Did you get the PM I sent you about shifting the main and auxiliary transmissions? I learned to use a 5X3 setup in a B-73 Mack about 35 years ago. Mack called it a "Tri-Plex" and it was actually two transmissions in a single housing, using two separate shifters. They also had a 4X4 known as a "Quadri-Plex". With a little practice, you can learn to make just about all the shifts without using the clutch, just matching RPM between gears and making shifts with no gear grinding or damage.
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!