I bought an older Jacobs 14N Super Chuck off of Ebay a few years ago. The chuck was in great shape with virtually no wear, but wow was it hard to turn: very gritty. I finally decided to pull it apart and clean it.
I made some custom arbor spacers on the lathe so the actual chuck disassembly was quite easy. My press, Big Orange, had no trouble separating the chuck parts.
I forgot to take a picture with the jaws & balls removed, but here you can still see that the factory grease had turned into the consistency of dried-out ear wax. Yum! It's a wonder it would open and close it at all.
And here we are after a few hours in the parts cleaning can, some wire brushing and all the parts ready to go back together.
Now the chuck's all cleaned-up and back together, just like a new one and ready for some heavy drilling in the mill. It works so much easier now it's a pleasure to use.