89 k2500 rancher

i have a 1989 K2500 . i have a strange almost squeaky noise.. best way to describe it is... it sounds like an old screen door that creaks when u open it slow.. it starts doing it around 25 - 30 mph. and it sometimes changes when going around a corner. it doesnt do it all the time. but it is starting to do it more frequently. the noise doesnt change pitch at higher or lower speeds.frontend shake down only thing was loose was left front lower ball joint.. and wasnt really that loose.. any help would be much appreciated
thanks