make obj1: thats the body of the car
make obj2: that`s the wheel, so it`s a sphere
go to joint object -> enable -> cross at 1 and 2 (always 1 for the body and the obj numver of the wheel) -> upper and lower rotation are both 0 -> rotation axis (with this you can say where it is driving) is x: 0 - 1 ; y: 0 - 1 ; z is always 0.
the strengh should be kind of high and the speed rather slow.
you need to make at least 3 same wheels so your doesn`t fall over.