The tilt spool will have a check valve either internally fitted in the spool or externally in the pipe work. This check valve is to prevent the drift forward as the pressure is matched in the system to the pressure in the tilt rams. The lift spool has a similar single acting check valve to prevent the mast dropping as the pressure is matched when you go to lift. 3rd and 4th slices are not normally fitted with check valves and using either one of these slices to run the tilt could cause a problem and would not be the best way forward. I would recommend if parts are available replacing the check valves in the tilt circuit or replacing the tilt slice.