I've backed off the castellated ring on the steering column end and the ally box nut thingy will undo anti clockwise but there appears to be no more tightening left

The top adjuster does make a noticeable difference to the stiffness so I've firmed it up slightly but that's not my main concern really.
Can these boxes be rebuilt? Is there a kit available so I could do this or is a professionally built box the way forward? If so, any suggestions. I haven't considered a new box cos I'm guessing that's expensive but if that's what's needed

Cheers guys
