kislon

We own a 2007 Outback and had to replace the Head Gaskets 2 years ago with only 85,000 miles on the car for about $2200 (plus timing belt, etc. for a grand total of $3k). Now less than two years later, with 111k miles, we are being told that the transfer case may need to be replaced based on the rattling sound under my hood, for another $2500-3000. What in the world? This is our first Subaru and I am very disappointed. Is this normal? Does this sound correct? Is there something else that could be wrong? Does anyone recommend getting a "used" transfer case if my mechanic can find one? Any advice is much appreciated!