Having owned three 124 cars and a 126 and adjusted all of these for steering play, I learned quite a bit:

-Sometimes the box is simply worn out
-When adjusting the box, you can over tighten, crush the mechanism resulting in a worthless box (Don’t ask me how)
-Adjust slowly and avoid the binding/ over-tightened result at all costs. (the steering does not self-center itself when driving around normally).
-I was told to adjust with the wheels off the ground. I did not ever determine why this was necessary but it did seem to help.

On the old 79 240D, I did replace the box after checking out several used boxes at a junkyard. Also, the later boxes do seem to be better and the adjustment goes easier.

Although all these series cars have free play, I was able to resolve the free play issue to an imperceptible / acceptable range.

Hope this helps,

Haasman

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'03 E320 Wagon-Sold
'95 E320 Wagon-Went to Ex
'93 190E 2.6-Wrecked
'91 300E-Went to Ex
'65 911 Coupe (#302580)