I just got an 05 GMC 4x4 CC SB D/A and like many others Im new to diesels. I will be towing a light travel trailer and drive the truck as a daily driver. So what do I need to know during my initial break in period that isnt in the owners manual? When should I make the fluid changes? Whats the deal with differential fluids I keep hearing about? Can someone get me up to speed on the basics for the new guy? Thanks in advance for the help, Joe

Welcome to the Place. dmaxallitech developed a maintenance schedule that should pretty much cover anything that you are willing to do. You can find that here:
http://www.dieselplace.com/forum/showthread.php?t=33348
Break in is pretty much up to you. I think they say no heavy towing for 500 miles with breaks in between to let the rear gears cool and after the 500 miles with towing take breaks again to let the rear gears cool. It is up to you. The better you maintain your truck, the better it will most likely be in the long run.

Acquaintance of mine who makes his living as a mechanic says a common mistake people make is not changing out the Automatic Transmission Fluid frequently enough. He claims that if it is done at 25,000 mile intervals a lot of down the road problems probably won't occur. Doesn't matter what make or model. 25,000 miles is the magic number for AT longevity in his book.

Grease it today, and check all fluids you will find them short - front end, rear end etc.