Did you figure out the issue? I was hoping someone with a little more intel than me would chime in. From what I see, the LK 3504 uses a similar steering unit as the one on my LK 2554. So the adjustment you are referring to must be the one on the back side of the output sector shaft?
Did you remove the sector shaft?
When I replaced my steering column seals and bushing, I did not remove the sector shaft. I did however, replace the sector shaft and have had to adjust the backlash on the gears. What I did was adjust it up till the steering wheel would move the sector with the slightest movement. Then back off to give just a little play. Haven't had any more issues with the steering and that several years ago.
Hope you get it going!