</font><font color="blue" class="small">( I had installed the filter right in front of pump on return line.)</font>
OK, now I am confused. You located a filter near the pump? Either scenario that easilly comes to mind are both bad. If it is on the suction side, putting a highly restrictive filter on a pump suction can be real hard on the pump. The only type filtration that I have ever come across on a hydraulic suction side(without the use of a feed pump) is #100 mesh screen. This filters to about 150 microns and flows relitively well with little back pressure/restriction. A typical hydraulic filter is a cellulose media that filters as low as 10 microns. Most hydraulic filters I have experience with were designed to feed the oil through with pressure and not draw it through with vacume. Most filter assemblies incorporate some sort of bypass that opens and continues to feed oil if the filter differential pressure exceeds a preset limit(10-15PSI) such as when the oil is cold or the filter is clogged. Using this deffinition, a mesh strainer(such as originally found in the resovoir) is generally accepted as being OK. A regular filter on the inlet would be hard on the pump, restricting flow and cooling, and increasing supply line vacume inviting the induction of air into the system at the slightest leak in supply line or pump seal. Bubbles through a pump also cause cavitation which leads to metal wear/erosion.
A filter on the pump outlet, unless speciffically designed for the pressure, would just rupture.
Most filters are found just before the fluid returns to the resovoir, down stream of any high pressure.
They do make spin on strainers(metal can with #100 mesh inside). That on the pump inlet line should be OK, or at least as OK as the original filter, providing it is clean.
I would say as a test, take that add-on filter out of circuit and see how it works.
Unfortunatly the main flow on most of these tractors is back through the 3PH lift valve and directly into the resovoir. This leaves no place to easilly plumb in a return line filter on the LP side of the valve.