Check This Out

The wife has a 2001 Kia Sportage...been having issues with the 4WD...said it was "popping". She took it in to the delaership...and they finally got it this time. She didn't even have 4X4!!! It was more like 3WD!! One hub would not engage at all...the fix...basically a whole ne front end...apparently this is a common problem on them, and they have "kits" for the older models...basically a front axle with all the fixins...in a box! THANK GOD FOR THE WARRANTY!!! $1600 worth of work.

Yes the vacuum operated hubs on the 1998-2001 models, although an interesting design, is a source of problems specially in cold weather. In Canada, Kia uses to remove the vacuum hubs and replace them with auto-mechanical.(only on complaints, not systematically...while they should). This can be seen by the hub caps requiring to be cut to let the new hubs protrude a little, cause they are longer. Is this what they did?
A common problem linked to the hub problem is that moisture "inhaled" by the vacuum contaminates the front bearings so may be they changed the complete bearings and suspension strut?? Since the front end is an independant front suspension, there is no "front axle" as such, so it would be interesting to detail the parts they have changed. What you describe seems extensive and it is good to have all know about it.