In this thread there are two references to Spider gear or spider gear shaft. I can not find any pictures of this so can someone make it clear to me what that is? Is it on the axle or differential and where so?

YAK: Check those allen bolts on the inner part of the right axle. On mine, I was shocked to find they were very loose on one of my axles and not the other. I could squeeze the boot and and hear a hiss (air leak) and it turned out to be a gap in between those metal plates that those allen bolts hold together. I tightened them up and the hiss went away when I squeezed the inner boot. This might be the leak and if it is, by the looks of it, you have loss some grease in there and might need to repack it.