Im a few years late to the party, but this is one of the first threads that pops up on google on the subject of these bearings.

I just had to displeasure of replacing some massively destroyed bearings on these hubs, and it was a nightmare to say the least. Partially due in part to my lack of tools, parts and know how when it comes to replacement. I rode more miles than i can begin to remember on a bad set of rear bearings and when i did finally replace the, they were in 4 pieces, not counting any ball bearings. I highly suggest that you replace these as soon as they start making the tell tale snap, crackle and pop. I spent damn near an hour trying to get the cracked outer casing of the bearing out of the hub with as little impact on the hub as possible, it was a hell i would not wish on my worst enemy. In the end, i managed to pry them out using a lock ring removal spanner, but marred my hub in the process.

For anyone who might stumble on this thread as i did, replacements are Enduro Max 7901 sealed bearings, which can be found with a quick search on amazon for about $5 a piece (I got mine through Niagara Cycle in Niagara Falls NY, within a week of order even though i had to get them shipped to an APO Box in Korea which typically takes longer than normal USPS shipping). Good luck changing these bastards, they're a real treat.