If you're making a slow 4 legged walker (AT-AT or Mammoth Mk. 2) I'd give it mammoth tank physics, so it handles like a tank with invisible treads. Then just make 4 animated legs. And bingo, you have what looks like a walking vehicle. It's near impossible to make a realistic walker with 4 legs that work like legs, the tread idea is all I could come up with to compensate. Good luck