Before you buy more, I just wanted to mention that these hydrolic arms are known not to work as well in colder weather (ideal gas law, PV=nRT). If the problem began when the weather got colder, then that is your problem, you can't do anything about it.
However, if they have been gradually getting worse, you can find them on e-bay sometimes.
SOR carries them
http://www.sor.com/sor/cat139.tam?xa...x=cat139%2Etam
New ones are a bit stiffer and will help. I would just prolly buy new ones as used ones are going to give you the same greif.
ben