You could animate ONE tooth of the chain.
Make it a graphic first of all. Turn onion skin on, make a new frame. Put the tooth (the one on the new frame) right next to the transparent one (the one of the old one), and animate in between. You'll basically get a tooth moving to the left and that's it.
Now, if you put a bunch of these graphics together, you'll get the illusion of the chain moving.
Here's an example of what I mean: