JD 430 Loader Hydraulic Problem

[jgbanshee]

Just switch the Load Check valve for the up/down with the curl/dump valve. Nothing changed. I think that I could say that the Load Checks are good and working. While testing the loader just now up/down, the loader will not pick the front end of tractor off the ground like it used to. Finally I put the loader all the way down with the bucket flat on the ground and dumped the bucket enough to lift the front end off the ground. Went to raise the loader and it started to work like normal. I shut it down now and i will try it a little later. It has been awhile since the last hydraulic fluid change. Could it just be fluid and a screen cleaning?