[Bobcat]

One of the Divisions I used to work for made single acting hydraulic rams ... which these lift cylinders are . The chattering/squealing is caused by the seals grabbing the rod tightly , then breaking loose , grabbing etc . This happens very quickly , and normally under light loads . As the load increases , the system pressure required to move the load also increases , which reduces or eliminates the problem . If the seal material was changed or the seal squeeze/preload reduced , this would eliminate it .... the anti chatter additive also works as it reduces the friction between the rod and the seal . Rod surface finish also has an effect on this . I`ve seen it so bad on some presses that you could hear it from 30 yards away in a factory and feel the floor vibrate from about 6 feet away .