Damn, I must be psychic as I said 4WS axles cost that much earlier. You could buy an entire quadrasteer totaled truck for that amount and have all the spare parts you could ever need. I suggest you check car-part. I see some with 3.73 for less than $1000.
www.car-part.com
Special rear. They're on eBay for ,$3500.
I'd gladly go check it out, but it's a planned move...200 miles and through Philly to get there. That's a 5 hour trip. True it could be lots of things, but it's a car lot, and they might have a clue that they don't wanna fix it.