Abstract: A vehicle speed-dependent and engine load-dependent hydraulic control device for heavy vehicles shifting between two gear ratios is provided with a modulator valve modulating main input pressure by action of the engine load-dependent pressure, a shift valve shiftable by action of modulated pressure supplied to the shift valve from the modulator valve through a signal valve and a signal valve shifting down by the action of a spring and the engine load-dependent pressure and vice-versa by the action of vehicle speed-dependent pressure. The control device is further provided with a pilot shuttle valve controlling supply of the higher of two pressures, the load-dependent pressure and a limiting pressure to the signal valve to shift down according to the operator's command.