Thank you. I am still confused about how the clutch pack works - does it share a sump with anything else? Does it use transmission fluid or its own fluid? Is the front differential attached to it? I'm new to Subaru's version of AWD.
"Clutch packs" and "bands" are standard automatic transmission parts, usually used to control what gear you are in; this is done by locking together (clutch) or stopping rotation (band) of sections of the planetary gear set. They are main components of every traditional automatic transmission. No wiz-bang, space-age engineering here; just an inspired application of an everyday part.
A "clutch pack" is simply a clutch (a steel disk and a friction-material covered disk pushed together to transmit power), except that there are a stack of alternating steel/friction disks packed together.
The AWD parts are just standard automatic transmission components, and they are housed inside the tranny like the rest of the automatic's components. Lubricated by ATF, controlled by ATF from the tranny's pump just like the rest of the parts, and suffers similar to other AT parts (slipping, dragging, harsh engagement, too-soft engagement). You seem to be experiencing dragging/sticking.
The front differential is directly connected via gear to the tranny's output shaft: It is always driven. The AWD's clutch pack is mounted to the end of the tranny's output shaft (after that gear), and only powers the rear differential when told to do so by the TCU. (Technically, the control works backwards, but that is harder to grasp.)
Bottom line: The AT's innards are probably gummed up (very common with 4EATs), and the best course of action is similar to what "1 Lucky Texan" has suggested. Listen to him (or others with practical advice) and don't sweat the technical stuff too much.
Edited by NorthWet, 16 August 2013 - 10:54 AM.