does someone know how to make a Raycast car?
what is a raycast car ?
A rigidibody with 4 rays to simulate wheels.
Well, do just that then 
No, seriously: I never tried to with jME Physics but as it works well in ODE and rays are supported it should work well with jME Physics, too. Just try and report any problems back here.
Maybe reading this can help you to build the car.