how can I move a Gameobject along its global axis

Hello, I'm attempting to create a snowboard game. I'm having issues getting the gameobject "center of mass" to move along it's global Z axis as it spins around on it's Y axis (with the snowboard).

as of now the "Center of Mass" is basically just a cube that i want to move towards the front (nose) of the board when pushing up on joystick, and move towards the back (tail) of the board when pushing down on joystick. when joystick input = zero the "center of mass" returns to the center of the board.

the method below is working, but it only moves the "com" back and forward on it's local axis. How can I get the "com" to move along it's global axis?

Any help is greatly appreciated!

using System.Collections; using System.Collections.Generic; using UnityEngine;

public class ExampleScript : MonoBehaviour {

 public float rotationSpeed; 
 public float distanceToBinding;

 public GameObject snowBoard; 
 public GameObject com; //"Center of Mass"
 

 void FixedUpdate () 
 {
     Spin();
     LeanForwardAndBack();
 }

 void Spin()
 {
     float horRot = Input.GetAxis("Horizontal") * rotationSpeed * Time.deltaTime ;

     if(Input.GetAxis("Horizontal") != 0)
     {
         snowBoard.transform.Rotate(0, horRot, 0);
     }
 }

 void LeanForwardAndBack()
 {
     //rotate with the board
     com.transform.rotation = snowBoard.transform.rotation;

     Vector3 pos = com.transform.position;

     pos.x = snowBoard.transform.position.x; 
     pos.y = snowBoard.transform.position.y + 1;//move slightly upward
     //SLIDE CoM FROM NOSE TO TAIL (RECENTERS WHEN NOT PUSHING JOYSTICK)
     pos.z = snowBoard.transform.position.z + (-Input.GetAxis("Vertical") * distanceToBinding * Time.deltaTime);
     //THIS MOVES THE "CENTER OF MASS" ALONG LOCAL AXIS. I NEED IT TO MOVE ALONG THE GLOBAL AXIS!

     com.transform.position = pos;
 }

}