Originally Posted by ROBD
That's what I thought. It's synthetic like the GM fluid. Im curious in the condition of the old fluid.
I changed out the transmission, transfer case and rear differential fluid @ 41k miles on my '09 Outlook. The rear diff. fluid, by far, was the most degraded. The fluid was black, and the drain plug magnet had a "dollup" of black sludge on it. By contrast, the transfer case fluid was almost clear, and the drain plug magnet was virtually free of accumulated sludge/debris.
I used the GM 75w-90 fluid for two reasons - 1) Although Mobil 75w-90 is acceptable, I didn't want to change fluid manufacturer and in the event of a warranty claim (5 yr/100k powertrain), call into question the use of a non-GM fluid; 2) the GM fluid has an additive to give it a grape smell, which does moderate the sulfur smell to a degree.
For a DIY project, a manual fluid pump really made replacing the fluid easier. For the transfer case and rear diff., the fluid level is at "full" when it runs out the bottom edge of the fill hole with vehicle level.
Based on my experience, I'll be changing the rear differential fluid every 30k miles.