How to change axel bearings on 400ex.
Actually the hardest part is removing the axel nuts.
Here are some tips:
1) Loosen the axle nuts before anything else. If necessary, get someone to hold down the rear brake for you or use strap and some ingenuity to hold it down. You do not need to loosen the two nuts all the way off the threaded sleeve. Just far enough to get to the c-cip under the bell-shaped axle nut. Do not take the brakes off first or you can't use them to stop the axle from spinning. It really helps to order a set of axle nut wrenches. I got mine from Motion Pro. I had to use a dremel though to make one of them slightly larger so it slid over the bell-shaped nut.
2) remove the c-clip under the bell-shaped axle nut so the threaded sleeve slides down the axle.
3) Remove the right rear tire so you can remove the large nut on the end of the axle. Do this before removing the brakes too.
4) Once you do get the carrier out, just use heat on the carrier. Once it is hot (2-3 minutes on the first side), smack the carrier downward onto a 2X4 sitting on the garage floor. The weight of the metal sleeve spacer will act like a hammer and knock the bearing out of the carrier. Heat the other side and do the same thing. You never need to use a hammer or punch to get the bearings out.
5) do a search on this subject. There was quite a bit of detail on it about a month ago.