If you watch the video you will notice the crowd function hesitates as if a void builds in the cylinder just after he drops the bucket in the bottom of the hole. My 310D sometimes does this. Is it normal? http://www.youtube.com/watch?v=8uRWn0Mceow&feature=related
My 310C does that too - I suspect that the piston packing is bypassing oil a bit. It has been on the "to check" list for about 3 years now, but I haven't quite got around to it. The stick will also flop around a little if I happen to drag it over a pile of sand while moving the tractor on the tires. Not major, but I must address it soon as I want to do a complete hydraulic system service, and would like to get it cleared up too. I'm keen to read what others think it may be Deon.
It looks like the stick is extended and the pump can't supply enough oil to fill the piston side of the cylinder fast enough. It appears it is happening because the stick is extended out putting more weight on the cylinder. I would suspect the problem is hardly noticeable when the stick is all the way in. Usually the problem is solved with one of three types of valves. Older machines used what was called an anti-cavitation valve which simply just opened the piston side of the cylinder to the reservoir when a vacuum was experienced. Older excavators used these a lot. The variation on this is called a safety suction valve which just incorporates the anti-cav function in the circuit relief. The second type of valve is a restrictor in the arm circuit which just limits how much oil can pass out of the rod side of the cylinder. These usually work real well but do create heat and noise. The last type of valve is called an arm regeneration valve and it sends the rod side oil back to the piston side when there is a negative pressure. The hydraulic schematic will show if you have one of these valve and where it might be located. Good Luck
John C. I thank you for the detailed reply. I looked over my technical manual and can only find pressure relief valves in the valve body. Seems as if some of these relief valves may double as anti-cavitation valves. Would it be a good idea if I was to remove the relief valves to inspect them for damaged seals, springs of some thing?
I suspect that since it is a backhoe and not an excavator, your machine doesn't have either. In your schematics if you follow the return flow from the stick all the way to the valve, is there any other components? Does the valve spool itself look the same on both ends? I usually don't like to pull valve cartridges unless I'm sure the problem could be there.