Your truck should have a display (ECS) and it will show the gear selected and the direction, 1F for 1st forward. In auto the gear lever is left in 3rd and it will start off in 1st or 2nd depending on how it is set-up and shift up as the travel speed increases. There maybe a setting you can change by scrolling through the display but I think you will need a code to get into the set-up menu's, this maybe available from Kalmar but I am not sure if they will give it out.
Steve.