My Chilton Manual says to use 80-90 wt. gear oil in my manual steering gear box. The (repro) owners manual I just bought says to use a Ford proprietary gear grease.
What works best based on your (long term owner's) experience?
My manual steering gear box filler plug has a "vent" opening. Is this indeed a vent that should be kept clear? I seem to remember (from way back) these holes were for a wick of some sort.

 

This was a recent topic of discussion at Slick 60s. Gear oil works ok but since a lot of these boxes have leaky seals by now plain old bearing grease is also acceptable (and won't leak out).

 

I filled the box with 80-90 wt. gear oil and made a simple cloth filter for the plug vent. So far no leaks. Steering feels good.