Drove a Syncro into some soft sand and got stuck. Both front and rear differentials were locked. Aired down to 20 psi. Had to pour water on the sand and people pushing too. Everyone says I needed to go down to 10 or 15 psi for soft sand. But we got to some harder sand and drove out so did not test lower pressures. I will try 10-15psi next time.
In the slow-motion part of this video you can see that the front wheels turn ~20% less than the rear due to slippage in the center "diff" which is actually a Viscous Coupler. There is a product that can be used to delete the VC but then the van becomes a "4WD" instead of AWD. Which has pluses in sand for example, and minuses on snow, ice, gravel. An "AWD" is easier for most people to manage.
Upon returning home I did some tests on the Viscous Coupler, and by the ":established method", it seems "OK". This van also has F&R Peloquin differentials, which are a worm-gear-type of LSD.