Your transmission should start in first gear. The vacuum valves on top of the VC (as Dr Parts describes)initiate the 2-1 downshift as the throttle is taken up (before actual rpm increase).
Unfortunately the 80-81 240 and 300D only had vacuum shift; no control pressure cable. After the valves at the VC are working the shift points are changed by adjusting the length of the linkage from the proportioning valve to the throttle. (on the rear of the pump)
Bosch Master, ASE Master, L1
33 years MB technician