I have a 1985 500 SL - Grey Market, with a lotta play in the steering. It was adjusted by a competent shop but they said that the box was in bad shape and could not be adjusted fully without risking locking up. Can these things be rebuilt? I can get a used one at a reasonable cost but there is no way to really assure that it is any good until installed and tested with a load put on it. Any help appreciated.