It’s Magna Powertrain that specified the Dex VI when they won the contract to supply transfer cases to GM back around 2007 or so. They haven’t changed to anything else in the fluid spec since then. The Auto Trac version does contain some friction discs.
Here is the GM Authority take on the latest 10 speed Allison. I would suspect the sales people have no vested interest to tell potential buyers that “ it’s not really an Allison “.
I took a bullet for the Bitog team and visited my local Chevy GMC dealer. A friendly salesman walked me over and let me take a pictures of a 1500 and a 3500 VIN. After thanking the salesman I went to the parts department, explained to the gal what I was up too, and this is what she found. As usual they only need the last 8 digits of the VIN.
The 1500 pickup was : RZ334376 It identifies as having a 9.5 “ ring gear and its factory fluid is 75W85.
The 3500 pickup was: R1190371 It identifies as having a 11.5 “ ring gear and it’s factory fluid is 75W90.
She didn’t invite any discussion on asking me what my intended use was etc. I am satisfied they don’t post it in the owners manual to keep ya-hoos from getting it wrong. Maybe in some west Texas town some parts guy might try convince you to use something else but that’s up to the dealership. The fluids are identified in by typing in the last 8 digits of the VIN. Nothing more complicated than that.
