i'm not sure exactly what caused it. one day it started getting just slightly jerky as i was going down the road. the jerkiness gradually got worse over the course of a couple of weeks. i thought it was a driveshaft problem at first, then t-case and then i pulled the diff cover off to find it was split like that. it still drove ok, was just a little jerky going down the road.
mine had the similar outcome, seemed jerky and then i got out of the trail turned right and heard a big bang, lugged it home and pulled it apart, chewed up the spider gears and hairline fractures all around the carrier.