You probably have grass build up in the little gear, Part# 1

Both bolts are the same PN, so I'd expect conventional threading on both.

Look down the forum a ways for a similar post.
Nevada Walrus posted some caveats about part #2 & 3? IIRC, installation was specific to each side???

Here's the link I referred to-

http://forums2.gardenweb.com/forums/load/lmower/msg0419465232625.html?9

Here is a link that might be useful: Link

Can't help but think the poster has the wrong model listed. The shaft should not turn with retaining bolt on this model and even if the rare chance that one broke its weld I rather doubt both sides did.

I kinda think he must have one of the models that uses the larger ratchet inside the wheel hub and wheel mounts direct to the trans shaft. These will turn with the retainer. In the shop the use of an air gun will loosen them but using a hand wrench requires locking a pair of vise grips to the trans axle under the deck to stop rotation.