Abstract: Control device of an automatic transmission having four forward speeds with shifting under torque together with a hydrokinetic torque converter with an integrated torsional damper, and one reverse speed, of the type comprising a planetary gear train controlled by three clutches and two brakes with hydraulic control. A hydraulic distributor controlled by four solenoid valves selectively feeds the clutches and brakes, depending on the running conditions of the vehicle. The control means of the solenoid valves are made to use two states of one of these solenoid valves to allow fast filling and progressiveness of the active receiver or receivers during shifting and two states of the other solenoid valves to assure the various sequences during shifting.

Abstract: Pressure control device comprising a manual valve (VM) associated with a pressure control valve (VRP), includes a first line pressure (P.sub.L), defined by two calibrated jets in series, which are placed on a duct set at zero pressure by the manual valve (VM) being in a first position R. At a second line pressure range (P.sub.L), a duct is fed at line pressure (P.sub.L), the manual valve (VM) is in a second position A. A variation of line pressure (P.sub.L) is assured by a modulating solenoid valve (EVM), which establishes a modulated pressure (P.sub.M) acting on a differential section (.SIGMA.) of said pressure control valve (VRP).

Abstract: Two-level pressure control device has a pressure control valve VLP 3 associated with a system of jets and in series to obtain a first reference pressure level P.sub.1 and a second reference pressure level P.sub.2.