Lift pads only semi operational

[Catenary Kid]

I have a 1968 JD 350 Crawler Loader with a backhoe. I got it from a friend who went through a divorce. It has as many issues as his marriage did and I have a bunch of questions. First: the loader was sitting in a fencerow disconnected (of course) from the loader. When we hooked it back up we had a lot of trouble getting the hydraulic foot pads to lift the hoe to line it up and hook it to the loader, but we eventually succeeded. I have attempted to use the loader (just to work hydraulic fluid through it) to move some old logs but can't get the pads to lift the back end of the loader. They will distend to the ground and put a small amount of pressure - enough to slightly move the back of the loader upwards - about 2 - 3", but will not actually lift the loader. I have filled the reservoir (overfilled initially) with fresh fluid, and have worked the arm, bucket and pads repeatedly, but can't get sufficient lift on the pads. There are leaks all over the crawler, but none in the pads that should affect the lift. So: Where do I start with this? BTW: all the rest of the hydraulics work reasonably well and I can lift the front of the loader with the bucket just fine. I can also lift the back of the loader if I use the bucket on the hoe. Suggestions?