[914x4W150]

Shifting between 2hi and 4hi basically just locks the front driveshaft in at the same ratio as the rear. when shifting between 4hi and 4lo, it is actually engaging another gearset to reduce the gear ratio in the transfercase. Loud grinding indicates shift fork is not fully engaging, or gear damage, which could take out remaining parts andnleave you stranded. Best bet is to get transfer case to knowledgeable mechanic for teardown and inspection, unless you are mechanically inclined. Nothing magical inside, just gears and bearings....