Replacing tires on quattro

[Trey Donovan Drake <trey@sportos.com>]

I have an 85 4kq and I just replaced the front tires, but not the rear
ones.  One of the front tires had been damaged so I decided to get an even
two for the front, but the rear ones are not badly worn, only 10k miles on
them and plenty of tread.

The guy trying to sell me tires informed me that it might be harmful to
the transfer case to have dissimilar or older tires on the rear, and that
I ought to replace them all at once.  Is this true, even if the rear tires
are in pretty good shape?

-trey