the action of the one way clutch c0 rendering the first speed gear train g1 substantially inoperative if the second speed clutch c2 is disengaged and the third speed clutch c3 is engaged instead the driven gear 22 is connected to the output shaft 6 to establish the third speed gear train g3 while if the third speed clutch c3 is disengaged and the fourth speed clutch c4 is engaged instead the driving gear 23 is connected to the input shaft 5 to thereby establish the fourth speed gear train g4 on the other hand if the fourth speed clutch c4 alone is engaged while the selector sleeve s of the selector clutch cs is shifted to the right or reverse position the driving gear 25 and the driven gear 27 are connected respectively to the input shaft 5 and the output shaft 6 to establish the reverse gear train gr thereby allowing transmission of torque from the input shaft 5 to the output shaft 6 through the reverse gear train gr the torque transmitted to the output shaft 6 is then transmitted through an output gear 28 mounted on one end of the output shaft 6 to an enlarged gear dg of the differential df referring now to fig2 illustrating a creep inhibiting device according to a first embodiment of the invention the oil hydraulic pump p sucks operating oil from an oil tank r for pressure delivery of same to fluid lines 29 and 94 the pressurized oil from the pump p has its pressure regulated to a predetermined value hereinafter called 34 the line pressure p1 34 by the regulator valve vr.