Recently bought a 93' 440B. My problem is the lift arms are jumpy, like the pump is cavitating or getting air and it foams the hyd oil. Even after cycling many times. This machine has had a history of this. The previous owner bought it in 99' and said it did it since he had owned it, he just put up with it. The hydrostatic drive seems to work fine. I put a new engine in it [old kohler was blown up]and while out, i put a kit in the hyd pump being aware of the foaming problem. It didnt help, still works the same. It doesnt make the machine unusable just a nuisance. Anybody else ran into this problem. Also seems everybody on this site says to use 10w30 motor in the hyd system. Is this correct? I'm sure the machine has tractor hyd oil in it. Lots of equipment calls for motor oil and hyd oil is ran in it with no problems. Ex: Ditch Witch calls for 30wt motor oil and we always ran hyd oil in them with no issues. Other equipment calls for motor oil in the hydrastatic drive units, so i think i'll change the oil to 10w30 and see what happens. Just don't feel confident this will fix it. Any thoughts would be appreciated.