Tiny,
Don't know if it's much help, but I talked to an old guy from our car club tonight about the Columbia rear-ends. He tells me that your buddy's is likely a vaccum unit, although the earlier Columbia's were mechanical.
His advice was if it's stuck in high, make sure and check the level of the gear lube. While I'm not familiar with them, he tells me there can't be too much that can go wrong with them.
