Yes, you are absolutely right about the amount of my parts. This is the first real technic build I'm doing, however I've got a good few boxes of Lego City and have got three home-made differentials for the car, but they would not fit very well between the tires. I think I have the mechanics solved pretty much but the rear axel doesn't keep the tires straight horizontally and they twist back and forth during driving, witch I take to mean that its not strong enough and should be re-enforced.