It's not fully working. Nevertheless, it shows how to create joints (you could also have checked back the physics tutorial for that).
The idea there is to put acceleration and decceleration on the backwheel.
It doesn't take the angle of the carbody into account for now, I'll leave it up to your good care.
The rotation of the carbody seems buggy too, but is some sort of possible implementation to implement a motorcycle behavior like in motoX for example.