I wouldnt call it junk if it made it 85,000 miles, lots of people only make it to roughly 100k miles before a problem and at that point it's lived a good life for a part that wears 100% of the time you drive it.
It's just a known issue and many cars that GM made have them. The other likey problem was heat, 04+ cars transmissions run alot hotter and that will reduce it's life. Stinks for you but it looks like you'll need to have it rebuilt.