...the wheels. Meantime have a look at some of the detail in the 'cabin'
...a nifty little steering wheel (excuse the blu-tak!)
...and look at the detail on the inside of the door - including a 'viewer' (sort of explains how the Warthog 'sees' too) which is obviously linked to the camera (s) on the roof piece that fits between the doors.
I think this is how the axles fit (won't know if I've got it right until the wheels arrive) - Jed is putting together instructions for building. It's not overcomplicated just a little 'fiddly'