Patent US 5,772,555

A controller (100 in FIG. 1) for relieving a gear shift shock in a vehicle, comprising an input torque calculation portion (131) which calculates the input torque (T.sub.t) of the stepped automatic transmission mechanism of the vehicle from engine r.p.m. (N.sub.e) and turbine r.p.m. (N.sub.e), a shift start recognition portion (134) which recognizes the real mechanical shift start timing of the stepped automatic transmission mechanism in accordance with the change of the input torque (T.sub.t), a line-pressure correction magnitude calculation portion (142) which calculates a line-pressure correction magnitude (.DELTA.PL) during the gear shift operation of the stepped automatic transmission mechanism when the shift start has been recognized, a standard line pressure calculation portion (143) which calculates a standard line pressure (PL), and a command line pressure calculation portion (144) which adds the line-pressure correction magnitude (.DELTA.PL) to the standard line pressure (PL) and which delivers the resulting sum to a valve (52) for controlling the oil pressure of the hydraulic circuit of the stepped automatic transmission mechanism.