a u2266 p a 39 in fig4 at the high temperature is decided by the formula 1 after the duty coefficient is changed and the b 1 oil pressure draining time has been accomplished k the duly coefficient u03c4 2 is changed to u03c4 1 1 and the shifting is accomplished when the oil temperature is over the predetermined value the oil pressure characteristics of the c 2 clutch oil pressure and b 1 brake oil pressure are shown as a dotted line in fig4 and the torque characteristic of the output shaft is shown as a dotted line in fig5 the change of the dotted line is smaller than one of the full line therefore the shift shock is reduced for example the oil pressure p a at the changing point is 1 4 kg cm 2 when the oil temperature is less than 80 u00b0 c and a p a value of 1 7 kg cm 2 at temperatures over 80 u00b0 c is best for a reduction in shift shock the invention is used not only for the 2 u2192 3 shift timing valve but also for the other shift timing valves ex 1 u2192 2 shift timing valve 3 u2192 4 shift timing valve the principles preferred embodiments and modes of operation of the present invention have been described in the foregoing application the invention which is intended to be protected herein should not however be construed as limited to the particular forms disclosed as these are to be regarded.