[blucar]

In my response #10 to the shifting. etc., of a Columbia I clearly stated that shifting required a momentary release of the clutch, this is true of the up and down shift. I don't recall if the early mechanical shift controls had a clutch safety switch, I know the '46-48 electric over vacuum had one, that was energized when the clutch was depressed.
The shifting process also required the momentary release of the throttle, which increase's the vacuum pressure and minimized the torque on the drive line.
I do not see how a Columbia could be properly shifted, with the vehicle jacked up with the hand throttle set to 20 mph and the gear train under power.
If a '46-48 Columbia is in the OD range and an attempt is made to shift the trans to a lower gear, the minute the clutch is depressed the Columbia down shifts to low range which puts the trans in 2nd gear. Shifting the trans to high gear results in the OD staying in low range, until it is shifted to OD.
In reality the Columbia gives the vehicle six forward gears if the operator wants to use them.