Anyone know much about 4X4 auto hubs? (Have problem)

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I just took my 87' V10 out today and got a bit of a scare. It has automatic locking hubs and I rarely use them. It was in 2H as usual, and I left the house today and got about a block away and heard a sound that is best described as what you hear when you are grinding the gears on a manual tranny and then a sound like a transmission being dropped into gear. It sounded like the left side and was pretty loud so I pulled over. I wasn't sure what to do, so I came back home. Tried taking it around the block a few times and it did it 3 more times, so I just figured I better park it. I should add, when you here the "clunk" that's when it stops.

Anyone know what I should check for? It's not my daily driver, so It's O.K. being out of commision for a bit, but I obviously can't drive it like this. I also am assuming the hub is the problem here just due to the sounds and where it sounded like it was coming from. I have a feeling this repair is beyond me and there will be a big check to some shop in my future. GRRR!!

Any advice is really appreciated. Thanks