need front end help!!

[mactownvr6]

ok so I replaced my axle, but when I went for a test drive, there is some kind of clunking sound over and over when I get to about 15mph! I went back and checked to make sure everything was tight and put together right and sure enough it was. I have no idea what the deal is, any suggestions? I havent had it aligned yet would that help? I know a drive shaft is best when bolted in the same bolt pattern as before and needs to balanced... what about an axle?