The Yilgarn region starts about 300km NE of perth and is an ancient region even by Australian standards meaning all geological features have been worn flat over time with the exception of areas of rock hard granite and ridges of Banded Iron

On the edge of the weatbelt a side trip to Elachbutting hill is always worthwhile. In my opinion this is a more immpresive rock than wave rock (except without the resort and pay too see – well without much except a basic free campground)
I spent time checking out the rocks waves

http://forums.overlander.com.au/viewtopic.php?t=65802

If you're like the majority of 4x4 Drivers, you won't be able to change the diff oil until you get home, because you won't have spare oil and a sump pump to change it. If you suspect contaminated oil (a deep water crossing without extended diff breathers or perhaps you have leaking diff seals) then you can try and remove the water by draining the diff until only oil comes out the drain hole. Do not drain too much and leave your diff short of lubrication. Collect this oil and water emulsion as you should never dispose of oil into the environment. Save it till you get back home and dispose of it properly. Its not only diffs that can have water contamination, but also your gearbox, transfer case and engine oil. However, it is usually only when a vehicle is stationary in deep water that these components are contaminated.