03 39 x schwing.

the pump has been great till this week.  It is struggling to pump a 5 slump or less and when it is struggling it makes the boom move all over.  It is really hard on the guy on the hose.  We noticed if we lowered     the rpm and wet the mud a little it pumped better but still not right.  Any help would be appreciated.  Also it never pressures out, just acts like it wants to.  Thanks in advance.

sounds like a concrete issue , a substandard mix , this has a lot to do with the way a pump acts while pumping ,

I think we have figured it out.  seems like we have some dirty hydraulic oil which is plugging up the volume control.  Took apart the volume control today cleaned it put it back.   caddied the oil a couple times to filter it and seem to be pumping okay.  Thankyou for youre replies