You might find some answers in this thread although the w115 and the w123 are different is some ways.
No kick down on 240d auto trany
Mine now runs like a new car although I may have it set slightly too aggresively, it is winding fairly good (no tach) when it shifts into 4th gear at 60 mph but it is smooth as silk and if I drive it easy it shifts into 4th between 30-40mph but it seems to have a relatively hard shift compared to the lower gear shifts when diving easy and all the shifts when driving hard.
Good Luck