Just bought a new to me 05 SUT. One of the first things I did was drop the tranny and t-case fluid and replace with Dexron VI. It's one of the best things you can do as the Dex III fluid is junk. Here is a link to show to HUGE improvement to Dex 6...
http://www.sandyblogs.com/techlink/2...dexron-vi.html