ok.. when i try and back up in my car, .. lets say i'm backing up and i'm about to stop so i just wanna roll back a few more feet, so i press the clutch in.. and when i do so it feels like i hit a brick wall .. i stop immediately.. but if i leave the clutch half way in i can reverse the whole way... why would my car stop so abruptly when i press the clutch all the way in..??