Water in a transmission is very very bad news.
I took a 722.303 to bits and found that water / coolant had mixed to form a really nasty sticky emulsion that got everywhere. The emulsion is very hard to remove - does not seem to drain with the transmission fluid (!) - stays inside and rusts parts.
See for example
http://www.peachparts.com/shopforum/diesel-discussion/323259-722-303-bits-photo-shoot.html
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Not good news at all for the transmission. Whilst the radiator is an easy fix - coolant hoses running to the transmission too - removal of a coolant and AFT emulsion is almost impossible (as far as I can tell) with out a total strip down.
You might find some product that says it will remove this - and perhaps this might be the one and only time (that I can think of) when a so called "flush" might help a tiny little bit for the larger parts of the transmission...
{disclaimer (!): On the whole the concept of a "flush" is in my opinion a load of old codswallop - I mean just look at the tiny passage ways: Particularly in a valve body where there is often a "no flow" hydraulic condition - no effing way any arse bucket "flush" is going to shift anything out of that!}