Just for clarficaion, because there is always some confusion about this: Dex VI is newer than Dex III. Dex III is NOT synthetic. Dex VI was introduced in 2006 and is a synthetic blend. It runs cooler and is far better than Dex III. It's backward compatible, and in fact GM recommends using Dex VI in transmissions that previously were speced to use Dex III. That's why the OP's shopped used it in his last fluid change.
As {tpc} said, brand is not important. I've used NAPA's brand of Dex VI in several vehicles. It's about a buck cheaper per quart than the brand name stuff.
{tpc} wrote:
I have an 07 but I used mobil one in the front diff, and lucas oil in the rear, because I couldn't find the right weight stuff for the rear in mobil one.
Interestingly enough, Mobil One's gear oil does not meet GM specs. I used it anyway on the front differential of my old Trailblazer.
Matt, the spec for what type of differential fluid should be used is listed in your manual. I hesitate to tell you what my manual says because you have the previous generation of truck.
