problem with new part

I just received the hub seal replacement kit from AppliancePartsPros and it all is complete except that I can’t get the new aluminum hub assembly all the way onto the transmission shaft. I have thoroughly cleaned the spines on the shaft and the new part easily slides onto the shaft initially but will not go all the way on (ie not far enough to be able to get the nut on the shaft). It appears that the hub assembly may not have been milled out completely on the bottom side. Any suggestions?