Well the same thing happened to me now.
Rugged Ridge Hubs are a piece of crap!!! I was wheeling at Pismo Dunes and after pulling someone that was stuck, I noticed I wasn't going anywhere like before. Turns out my drivers side hub bit the dust, and I was in 3-wheel drive. It was a real chore to get out of where I was, ended up having to get a couple pulls, and use my Maxtrax recovery boards a few times.
I think it was a combination of the soft/loose sand and the locker which "freed" up my hub. Haven't taken it apart yet, as I didn't notice any cracks or hear any noises driving back home in 2-Hi. I will do that today or tomorrow and try to add pictures to this post if I can.
I ordered a used pair of Aisins from ebay, which happened to pop up, usually they are pretty hard to find. I also ordered some AVMs to be a backup (also from ebay).
I was wondering if anyone has bought these new "Aisin" hubs that have been popping up on Ebay and also amazingly Amazon?
http://www.ebay.com/itm/Locking-Hub-AISIN-FHM-002-fits-84-89-Mitsubishi-Montero-/311126997276?pt=Motors_Car_Truck_Parts_Accessories&fits=Model%3AMontero&hash=item48709d391c&vxp=mtr
http://www.amazon.com/Aisin-FHM-002-Free-Wheel-Hub/dp/B00HFKEDVU/ref=sr_1_1?ie=UTF8&qid=1413833406&sr=8-1&keywords=aisin+fhm-002
I was reading online in some forum, can't remember which one, that these are Aisin copies that actually meet OEM standards, but not genuine Aisin manufactured parts. Just wondering if anyone has seen this on a rig or tried them out, I'm sure they must be better than Rugged Ridge, but I hardly think they would be as good as an original Aisin.
Sorry for long post, and sorry for whoever bought RR hubs after I said they worked fine for me, I take everything back that I ever said good about them. The one positive thing is they worked well for nearly a year, until I hit loose sand, and installed a locker.
So for normal street driving or casual offroading they should hold up. But any serious wheeling you should immediately replace.