I would be concerned that the high viscosity would cause slippage of your AWD clutch pack and reduce AWD performance. My understanding is the solenoid that operates the clutch works it's magic by being intermittent and thus an oil with different engagement properties could impair the expected performance.I'll probably be doing this sometime next year since I am at 14K miles and want to swap at less than 30K miles. I tow some and use my Yakima carrier at times.
I'll likely be using this for the front diff/transfer case & rear diff.