In a rod supporting portion 10e formed integrally on the upper surface of front bearing support plate 10A, a spring biased latching ball is disposed which projects into one of annular latching grooves 123N, 123F and 123R in the outer surface of shifter rod 120 for latching the rod at one of {HEAD ~ neutral and operative conditions} of {TAIL ~ the change mechanism} 6 
In a rod supporting portion 10e formed integrally on the upper surface of front bearing support plate 10A , a spring biased latching ball is disposed which projects into one of annular latching grooves 123N , 123F and 123R in the outer surface of shifter rod 120 for latching the rod at one of { HEAD ~ neutral and operative conditions } of { TAIL ~ the change mechanism } 6
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