Raycast problems!

im making a simple skateboard game with the design3 tutorial. the raycast code i have copied does not seem to work. i want it to tilt the skater as he goes up a vertical ramp to make it look realistic. i am a beginner in coding and even more of a beginner on raycasts. i dont know if my code is wrong or there is just something wrong with my model i am using. when ever i go up a ramp it doesnt turn then when i go back down the ramp it wont let me rotate the character left or right untill im on another ramp then i can turn the character but not on the flat plane for some reason. hope this all makes sense.

My code.

 var rotateSpeed = 90;
 var pushImpulse = 3.5;
 var maxSpeed = 12;
 var decayRate = 0.1; 
 
 
 
 private var character : CharacterController;
 private var trans : Transform;
 private var speed = 0.0; 
 private var targetRot : Quaternion;
 
 function Start ()
 {    
     character = GetComponent(CharacterController);
     trans = transform;
 }
 
 function Pushing()
 {
     speed += pushImpulse;
     speed = Mathf.Min(speed, maxSpeed);
 }
 
 
 function Update ()
 {    
     var horizontal = Input.GetAxis("Horizontal");
     trans.Rotate(0,rotateSpeed * horizontal * Time.deltaTime,0);
     
     if (character.isGrounded && Input.GetKey(KeyCode.UpArrow))
         Pushing();
     
     var moveDirection = trans.forward * speed; 
     moveDirection += Physics.gravity;
     character.Move(moveDirection * Time.deltaTime); 
     
     var ray = new Ray(trans.position + Vector3.up, -Vector3.up);
     var hit : RaycastHit;
     if (Physics.Raycast(ray, hit, 100))
     {
          targetRight = Vector3.Cross(hit.normal, trans.forward);
          targetForward = Vector3.Cross(targetRight, hit.normal);
          
          if ( character.isGrounded )
                  targetRot = Quaternion.LookRotation(targetForward, hit.normal);
     } 
 
     
     trans.rotation = Quaternion.Slerp(trans.rotation, targetRot, 5 * Time.deltaTime);
     
     
     if (character.isGrounded) 
     { 
     
     //Stops character when slowed down enough
         if (speed < 0.3)
             speed = 0;
         else
 
     //simple code to add friction to character
         speed -= decayRate * Time.deltaTime * speed;
     }
 
 }