Jon,
Good question, I am sure this is one of the most overlooked things on these old girls, "if it isn't broke don't check it" kind of thing. I looked through several books and same thing " Special Lubricant" Heck the Wallis 12-20 book I couldn't even find any reference to the steering box...
I'm guessing just a good greasing every now and then, It says every 60 hours in the MH 25 book with the special lubricant whatever that is??
I looked in the Massey Harris GP manual and surprisingly it says to use a light transmission oil in winter and heavy transmission oil in summer. this is the same gearbox used on the later Wallis tractors just the opposite worm gear.
Anyone else got suggestions?
Joe