Here's the latest. The wheels are separated from the skeleton. I added a target helper object to each wheel and each claw, and added a modifier to make the claw helper track the wheel helper. Then a few adjustments because IK made some strange leg positions. But all in all a lot easier than the old method.
http://www.ericdubois.com/3dsamples/mulefa/mulefa_walk8loop_3c.mov
Eric