Tranny swapability question

[Chris Stann]

>You'll have to do something about the rear diff. The 4kq has 4.11 gears and
the 5000tq has 3.888888888 gears.
>You can do it but you won't be able to lock the center diff without
destroying something.

Wouldn't the added stress of different front and rear ratios compromise the
life of the center diff even if it's not locked?  It would make sense to
swap the rear diff as well.  If it can be done.

Chris,
'88 Audi 90 with 350+K miles, and rolling...