replacing 4kq diff lock actuator

[Avram Dorfman <dorfman@est.org>]

Has anybody out there replaced the center differential lock actuator in a
4kq? How about in a urQ or a 5kq? I imagine they're the same.

I'm sure many of you have seen, or even have, 4kqs with differentials that
don't  lock. In my case, I've confirmed that the lock itself functions fine
if you reach under the car and engage it manually, and it's been confirmed
by a garage that it's the actuator that's bad.

Does anyone know where it is? How much is involved in replacing it? How
much I can expect one to cost both new and used? What is the part number?

I'd appreciate any help!

And yes, I'm sure that many of you have the same question, but no answer.
When I get an answer, I promise I'll post it.

-Avram
'87 4kcsq (for sale - www.est.org/audi)
'94 del sol VTEC
'00 S4