They were a solid built suspension that lasts a loooong time but they were hard to set the alignment. Have you had the alignment checked? How about any loose parts?
I worked at an alignment shop that had some kits that we put in to give them more caster. This is what we used. Northstar Manufacturing ::
The lower part of the radius arm had to be drilled larger nad this part was installed. The it could be turned for more caster.