I own a JD 455, recently purchased, it is about 10 years old. I love the machine, but I do have one problem with it, I can't figure out. When I am using the loader and have the weight box attached to the 3-point hitch, the weight box keeps falling. I have tightened the hydrolic valve under the tractor a lot, even replaced it thinking there was a leak somewhere. It didn't do any good. Someone said that if anything other than JD hydrolic fluid was used, this would also cause it. That sounds a little strange to me, though I do not know what kind of fluid is in it now. Any thoughts? Any info would be appreciated. Thanks.