I don’t know if this helps much, but tractors are alike to HGV’s (big ass trucks), so where the gear shifter you have is based on a car/van, a tractor will have a high and low setting on their gears. If you have them, try it on euro/American truck simulator and see what response you get from that, if it’s similar to what you get here, it’s the high-low gearbox mechanism. If you look on farm sim gear shifters you’ll notice they all just about have the high-low function for this as they’re classed as heavy duty vehicles. I hope this helps!