i got shimmy/vibration

i replaced my steering linkage the other day and the alignment iss/hould be right when im goin round fifty i feel a slight wheel vibration kinda like i need a wheel balnced but i kno its not that, when i step on the brakes it intesifies but im pretty sure my brakes arent warped. some time when im just decelerating the show f'n truck shakes and shutter like i dunno what.......im pretty sure i have a broken lower baljoint.....but would that cause that......help