80 series transfer case worry

Hi all!
After buying my father-in-law's petrol automatic 80 series with 265,000kms i have come across a potentially expensive problem... He has had it since new, had all manufacturer's services done plus serviced it between since he has towed a camper trailer around Oz a few times, and has never had a problem.
I decided to change all the oils, with them all coming out like honey and all clean sump plug chip detectors- excellent.... except the transfer case's sump plug chip detector had some seriously huge chunks of metal on it after clean oil drained out....
This cruiser has never been really pushed (driven by a 70yr old) and probably never even been in low range!
There are about 8 metal slivers about 2mm thick and range from the size of half a thumb nail to half that again, and a few shavings. They are ferrous of course, and look like a torn up washer or shim or tang or something like that.
She still drives beautifully with the later series viscous coupling seeming ok, no noises, and i gave her a run in low range to lock the transfer case (on dirt slowly) without any sign of a problem.

My worry is something serious is about to let go. My budget says keep on driving until it does or doesnt happen....
A trans shop said they have rarely seen an 80series transfer case with dramas, but will cost $1,500 and up for a rebuild if i remove and install it or $2k and up for them to do the lot.

Has anyone experienced or heard of similar damage and can anyone offer any much appreciated advice?
Thanks!