Lets see if this helps.
Modern heavy trucks with 2 or 3 speed splitters use the gears and splits together when they are under heavy load. ( light loads use less or no splitting)
That would be 1st low, 1st hi, 2nd low, 2nd hi, etc.
The trucks of this era, like your 2 ton, rarely split shifted because their ratios were so low to begin with.
On a paved road, you usually started in 1st (granny gear)high range and shifted normally.
If you were off road or starting on an uphill pull, switch to low range and shift through the gears until you reach paving or smooth ground. Then shift to high range and select gears as needed.
