Chevrolet Repair: Chevy Astro AWD hub bearing, chevy astro awd, chevy astro

Question
Hey Van:
I just got off the phone with the chevy dealer service department. I don't think they are trying to jerk me around or anything but here's the problem. I recently bought a 2000 Chevy Astro AWD from a private person. I also bought and took over the extended warantee (thru Chrysler Daimler). I have a rumbling noise in the front right side. (sounds like knobbys on a black top road) The dealer has changed the tires on the front, replaced numerous seals. did a "transfer case upgrade" (Sounds like this "upgrade" is changing the fluid several times and adding some magic blue stuff to the transfer case). Some of the stuff was covered by the warantee and some wasn't...my out of pocket expense is now up to $600+. The dealer says the noise is still there and thinks it needs a "hub bearing & seal". They contacted the warantee company and they said they don't cover that because it is an AWD vehicle.(They cover it for a rear wheel or front wheel drive, I forget which they said, but not for an AWD
  My question is what is a hub bearing, what causes a hub bearing to go bad within 80,000 miles, why wouldn't the warantee company cover it, (they cover practically everything else...the whole engine, the whole transmission, etc) is it something that does wear out frequently, is it true that this part is in excess of $900. The folks that I bought the vehicle from are in their late 60's and I'm sure didn't go Baha-ing with the Astro Van. I think I'm getting a bum deal here and would like to speak to the warantee company directly (which the dealer suggested I do) but I am not a wrench turner and don't know much about the subject I have to address.
Any info you could provide so that I may speak with alittle knowledge would be appreciated.
Thanks alot Van!
John Bee

Answer
Hi John,
If the extended warranty covers engine and driveline, then it should be covered, four wheel drive or not. The warranty was for that vehicle, and the vin number tells that it is four wheel drive.
So hold to your guns, and get it paid for.
It sounds like a wheel bearing to me.
900 sounds high.
Van