How to flush water contaminated diff oil???

Not really much you can use except keep changing the oil.
That is why if you suspect water has entered it is best to check diffs etc straight after the water crossing and drain the water out before it can mix with the oil.
all good in theory but hard to practise in the field ;-))
You may find that the reason the diffs sucked oil in with the breather extensions fitted is because the breather hose are too small diameter for the length, too much restriction to air flow and presto the diffs pull it past the seals.

G'day Tony,

You didn't mention vehicle make, but if the drain plugs are off-centre in the diff-housings (like Nissans), then I suspect that you're not getting all of the oil out each time you drain it...
The problem here (with water-contaminated oil) is that as soon as you stop, the water will begin to gravitate to the bottom, and this is what remains after you _think_ that you have drained the oil...

When I drain the diffs on the 'Trol, I jack up the opposite side wheel to where the bung is, & you'd be surprised at how much more oil comes out, compared to leaving it "on the level"...
Also, I always drain my oils after a good hard run on the highway (when everything's hot, & any contaminants are "in suspension").. Then, into the garage, & as soon as the engine is shut down, I'm under there with whatever I need to get them bungs out asap.. then give it plenty of time to drain...

re a flushing oil for diffs.. Would that CEM stuff work??? .. Alternatively, you might try a lighter grade oil 'till you've got it clean..

Good luck with it..

Regards, Ed. C.

Tony J,
Flush with pressurised kero. Will mean you have to remove axles.
Cheers,
Bros.

Tony J,
I had to do what i indicated after i smashed the rear diff to get all the fine pieces of metal out before installing the replacement diff. Even after doing this pretty thoroughly several times i was still getting minute particles stuck to the diff magnet months later after several oil changes.
Cheers,
Bros.

Never tried it but just as a suggestion pour some metho into the diff (with the oil in there) say 200ml and then give it a run to mix it. Then drain and refill. The metho should help the water mix with the oil and allow it to come out when you drain it. Not sure how it works with diff oil but it works with petrol and diesel. Worth a try if your going to drop the oil again anyway.