Purchased a piece of property and a backhoe that was not in running condition came with it. I got it running but have a problem with weak or slow operation of the backhoe boom and front bucket. When lifting empty front bucket will sometimes shake. It is operating with what I say is about 50% of the power in the hydraulics. Boom operates slowly but does operate. Fluid is ok, changed hydro filter. Any suggestions what it could be. It has been this way for some time, usable but not strong. Motor runs fine. Im thinking I need to rebuild the hydraulic pump. Looking for suggestions. Any way to test hydro pump before replacing?(1976 Model) I am not a mechanic, know barely enough to get by.