I might be wrong. I am just throwing this out there . I think maybe the gear selector's electronics might be messed up, or the transfer case selector is stuck in neutral (or 1/4 of the way in neutral, which might explain the grinding noise). The transfer case is put into high and low range by an electric motor instead of manually. The electronic motor could simply be non operational and the transfer case could have slowly slipped out of HI.... maybe lol. Try to shift it from HI to LO through the H-gate and see what the rover does (Going from HI to LO and then HI again might actually fix the problem ). I could be way off base and don not know enough on the subject to give a definitive answer, but I figured I would at least give my 2 cents worth.