I have an issue with my steering... (it is not the gimble)

I have play in my steering wheel and I have tracked it down to where the steering cable screws into the power steering unit. When you turn the wheel you can see the nut on the cable sleeve move back and forth an inch or so... I assume that is not suppose to happen? What is wrong? What do I need to do to fix it? (FYI, I have the grey steering unit on my 1997 502EFI with a B1)

Thanks in advance,
Mike