Hydraulics

[tw74]

My tractor is a Yanmar 2310d. I started having some problems with my front loader being "weak" a few months ago. Then the problem seemed to spread to my transmission. It won't engage normally in any gear. If I put it in gear and rotate the bucket all the way up and keep the pressure on for a few seconds the transmission will engage. Now this has gotten worse too and the last thing that happened is the box scraper was stuck in the up position. Over time, just sitting, it came down on its own. So since this seems to be a problem that affects the entire system, I have changed the fluid, checked the filter (my tractor only has the in line screen-type filter located under the tractor) and finally removed the pump. The shaft and housing seem fine and the pump appears to work smoothly but inside there are two o-ring type gaskets that wind around the two openings inside the pump. Those o-rings look too "flat" to be doing much of a job sealing anything. They are not broken or deteriorating but in places they do not extend above the groove they are seated in. I will admit that I am no mechanic but before I launch into taking the entire hydraulic system apart, I wonder if these two o-rings could be the cause of my problems and if I should replace them or replace the whole pump. Or, is there likely another problem elsewhere as I understand that pump failure in rather unlikely. Thanks for any help anyone can give me.......tw