Well, I was able to work the machine up to operating temp. The new valves work much better, but it seems like I still have drift on the swing. The loader has two swing motors, and I noticed on one of them is a rectangular piece about 5 X 7 X 1 inch thick where the two hoses come in. It has plugs at two corners and another one about midway on the top. It says Eaton, and 2000, and some other numbers that are probably model and serial numbers, but they're hard to read. I'm not sure what that thing is, but could there be a problem in there with internal leakage, causing drift? Or might the I have a problem with the motors causing the drift?
On another note, as I suspected, the old reliefs were probably not set at 1000 as it said on the cap. I have to knuckle in to lift the load, so might have to adjust that upwards.