How to prevent animator change Y position

I got a problem when using animator in Unity. I want to cast a ray from the position of the character to forward by using

 Ray ray = new Ray(transform.position, transform.forward);
 Physics.Raycast(ray, out hitInfo);

But when I check the "Bake Into Pose" in Root Transform Position(Y) the animator(Running and Walking) would change the Y position(even in idle state) and the Y axis would be lower than actual value and become negative. So the ray sometimes could not hit anything. But if I uncheck the "Bake Into Pose" the character would lose gravity. So how should I fix it?