This is why I was saying before not to worry too much about using the expensive synthetics in your diff. Save that stuf for the tow pigs and race cars.

Main thing is that you like to off-road and you run through water. If the axle tubes go under water, there is a chance that water gets past the seal, REGARDLESS of where the breather is.

It's cheaper to use the less expensive dino oil and just change it out. What's it take, 20 minutes. It takes me longer to change my oil, because of getting the damn filter off.

I used to do the same thing on my old truck and was running ARB's in front and rear.

It's cheap insurance to just change out the fluid, rather than leave it.