It's been a while, but if I remember right here's how to shift a Mack T2070.
Without a load, range selector in direct, shift it like a 5 speed, 1st is down in the lower left corner.
With a load, range selector in L,1st, 2nd, move range selector to D, back to 1st, 2nd, 3rd, 4th, 5th...