If you push out the hinge pins, do the cylinders advance and retract together and at much higher speed? If you have quick disconnects, look for one that's not seated properly. Also, try switching the raise/lower with dump connections and see if the problem goes with the hose lines. On my 80 loader, a pinched metal line on the cross tube was the culprit. Its either oil flow or a restriction. See if you can isolate it. If you have another cylinder lying around, try it on the dump circuit. I run quite a few different attachments on the loader lines via the quick disconnects. Even 1-way cylinders (as in mower header and cement mixer dump).