I am trying to make an object in one of my games stay paralell to the terain it is riding on, so say if I am going over a mountain I want to make it look like it is going over the mountain. Right now all I can do is use raycasting like this

 var fwd = transform.TransformDirection (Vector3(1,0,0));
if (Physics.Raycast (transform.position, fwd, 1)) {
   transform.Rotate(Vector3(-1,0,0) * speed * Time.deltaTime, Space.World);
}
   if (Physics.Raycast (transform.position, -fwd, 1)) {
   transform.Rotate(Vector3(1,0,0) * speed * Time.deltaTime, Space.World);
}
var rit = transform.TransformDirection (Vector3(0,0,1));
if (Physics.Raycast (transform.position, rit, 1)) {
   transform.Rotate(Vector3(0,0,1) * speed * Time.deltaTime, Space.World);
}
   if (Physics.Raycast (transform.position, -rit, 1)) {
   transform.Rotate(Vector3(0,0,-1) * speed * Time.deltaTime, Space.World);
}

but that does not allways work, and I was just wondering if there was a more efficient way to do it, it works ok but every once in awhile if I am turning at the same time the object flips and starts going out of control.