Probably the seal's leaking. Problem is if you get a kit to replace the seals etc, if there's any wear in the bore or in the housing itself you'll still have the leak. When they rebuild the box they check tolerances to make sure it's build able. Sometimes it's easier and safer to get a rebuild, new or an upgrade. When the weather breaks and I get a chance to drive the cj7 I'll find out if the lucus seal rejuvenator works. If not I'm upgrading to a AGR steering box.
Wm69 your busting my bubble. That's not good news to hear. Don't mind paying a little more for a good box (especially new without the problems of getting a bad rebuild which is happening more often). They use to have a good name and product.