Hello to forum. The car is a 92 300D 2.5 Turbo. On these cars the shifting of the transmission is controlled by two vacuum units. One of these valves is up at the injection pump and according to the manual it is called the vacuum control valve. The other unit is attached to the transmission and it is called the modulator.

I've read somewhere that the vacuum control valve at the injection pump controls the timing of the shift and the modulator controls the quality of the shift. Does this sound correct?

Thanks!