Windy

Hi. I was hoping I could get some help. I am building the Land Rover set but the gears don’t seem to want to engage. I bought the power functions so I could run it and try to spot the problem but I just can’t tell what’s going on. I’ve taken it apart twice now and I currently have it so I can see all the gears but it isn’t helping. I contacted LEGO and they said I should watch build videos but what I really need is a schematic that shows me what should be moving. Can anyone help me?