“ See your dealer” for advice on GM truck rear diff lubricant

[Snagglefoot]

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.

 

[Snagglefoot]

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 “.

 

[Rat407]

I just used AMSOIL Severe Gear in my 2019 differentials. 75w-90 in both.

 

[BobsArmory]

My
2023 GMC Sierra 1500 AT4 3 liter Duramax
Factory Specs
Front: 75W-85 Dexron Low Viscosity ACDelco part #10-4122
Rear: 75W-85 High Efficiency Synth Hypoid Gear ACDelco part #10-4091

I will probably go 75w-90 HPL or Amsoil severe gear

 

[The Critic]

My
2023 GMC Sierra 1500 AT4 3 liter Duramax
Factory Specs
Front: 75W-85 Dexron Low Viscosity ACDelco part #10-4122
Rear: 75W-85 High Efficiency Synth Hypoid Gear ACDelco part #10-4091

I will probably go 75w-90 HPL or Amsoil severe gear

OEM fluid strategy seems unusually "purpose built" for the application - sure you want to replace it with a one-size-fits-all solution?