[GRutter]

Don't fill your steering box with grease, then top it off with gear oil, as suggested in a prior post.
The grease is pushed out of the way, and at that point the grease serves no further purpose.
In an original sector shaft housing, there is an oil passage at the top of the housing that leads to the space between the two sector shaft bushings. Filling the gearbox with grease will likely block that passage and will stop the sector bushings (or needle bearings if modified) from getting the lubrication they need.
If your steering box is leaking from the sector shaft, rebuild it, or use a heavier gear oil - but don't fill it full of grease to stop it from leaking.