Regarding the servicing and maintenance of Sokkia AP41 and similar adapters, we have experimented with a variety of different consumer grade lubricants, including graphite, teflon based, silicon based, damping greases, gun lubricants, etc. but none of them provide the required lubrication for this application, but rather are too stiff or become that way over a short period, requiring excessive torque for operation. These instruments are used in the field in a relatively wide range of temperatures, and the lubricant must exhibit relatively little change in viscosity with changes in temperature.
Sokkia will not release the technical details of its lubricant to end users, prefering instead to direct end users for service at the dealer.
At long last, however, we have discovered a lubricant that is excellent for this application. It is manufactured by Leica, called D2m, part number 289964. The cost of this lubricant is about $35-$40 for a 1 oz jar. It should be stored in a cool dry place.