Traveled over 90 miles this morning with our 94 explorer in 4wd on hard packed snow, when I went to disengage the auto 4wd the front end made a loud thumping noise. I slowed down and stopped as soon as the highway let me, but can not see anything out of the ordinary. After working I got in the explorer and drove to the house that I stay at during the week. Only made it a couple of miles before a loud grinding noise started. Gets worse with wheel speed, but will not be there at all times. I took both tires off this evening, but still can not find the problem. Could it be in the front axle assembly, or would a bearing going out make this loud of a noise to cancel out the radio? Thanks for any help, I want to get home for the holiday on Wednesday, but that is 180 miles away.