Going synthetic all around is a good idea, especially if you forge water, etc...as the synthetics won't form emulsions the way the regular dino juiced versons will, and will protect the gears better if you get water in the diffs, etc. (The oil film stays on the metal instead of forming a foamy vinegrette, etc.)

One time I forgot to extend the diff vent tube on my synthetic filled jeep, and articulated under water, popping off the tube, and filling the rear diff with water...

When I drained the diff, hours later, the gears were still lubed/protected.

In the lab, we often ran tests that simulated water in the oil...and the results were pretty consistant...we could add additives to reduce the damage for the dino juice oils...but additives tend to coke out over time, and increase engine deposits, so it was always a compromise between water protection and deposits.