The British army did trials with and without grease in 101 CVs.
I dont know the results except for the fact that early in the trials the grease seem to be working well.
The top swivel in a 101 is a fibre bush and not a taper roller bearing like the lower swivel and like most other heavy duty off road vehicles.
Mine is running 140 gear oil with slight leakage.
The stuff to use is steering box grease made by Mobil.
It is a Semi liquid grease and this stuff is brillant.
It is hard to find.

