Wife's 2014 Silverado just rolled 5k miles. I usually do a flush of the front and rear diffs and transfer case at this mileage for peace of mind. Apparently GM in a quest for CAFE standards is now using a proprietary 75w-85 GL-5 synthetic rear end fluid as opposed to the old standard 75w-90 grape juice. Any body know if the rear ends are carryovers from the previous years? I always use Amsoil SVG in both front and rears of my previous GM half tons. Should I stick with the 75w-85 GM fluid? Only other 75w-85 I can find is Redline but it's GL-4 so that a no go.