From your signature I take it that the car in question was a 1979 240D.
That was the last year before the vacuum shift control. It only has throttle valve control (control pressure). There is a link running from the throttle linkage to a lever on the trans. The more throttle the later the shifts.
This tranny also has the electric kickdown. Bushings at the trans lever fall apart and can change the control pressure downshifts over night. Improper assembly of the linkages can affect this also. Its pretty straight forward though; shorten the link = later shifts higer speed kickdowns. Longer link = the opposite.
The modulator is fixed (one adjustment)on these trannies.