Sorry, can't help on the box adjustment. Have you tried a search on "steering box adjustment"? I know it has been discussed for many models, but I can't recall if the 126 was one of them.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.