I just got a 06 Duramax with 4wd. I had a 03 2wd Duramax and changed the read end oil at 1000 miles towing my 12,000 fiver and every 30,000 after that with Amsoil 75w-140w. No trouble with anything. I also changed the tranny filter at 5,000 and the tranny fluid at 35,000. Do I do anything different with this truck? How about the front grears and transfer case? I will hardly ever the 4wd as I am on the highway most of the time. I did get stuck with the old truck several times so I got the 4wd with this one. One time backing the fiver into a campsite and got off the rock and onto wet grass and everything stopped.
Tom:(

I would say change the front axle and transfer case fluids around 40-50 thousand. The front axle and t-case have parts that are still spinning in 2wd, just not under as much load as when in 4wd.

:exactly:

I would do the transfer case at 1000 miles also then every 15-25K. It only holds 2 qts and gets no cooling at all. When you change the transfer case oil it kind of looks like metal flake paint the first few times. It's your truck though so do as you please. My .02-