1. Has anyone/is it possable to convert the diff locks from vaccum actuated to manualy controlled via a cable ect...

2. Is it possable to just lock the rear diff w/o locking the center on my '87 4kq

You could use an electric solenoid or a long choke cable. You'd just have to fab up the brackets. In stock form no you cannot just lock the rear. I think the best and easiest thing to do is to get the diff lock control box out of a torsen car and hook up the diff locks that way, with electric switches. My master plan once i get my rear torsen installed is to control the center this way. yeah when ever i get around to that:)

I've heard of some that run 'rallycross' switch the front and center diff lock vacuum lines around at the back of the controller.

That way, first position of the control turns on the rear locks instead of the center.

The very early UR quattro's had cable operated diff locks. I can't see the advantage of going to cable if you have an existing functional vacuum setup..
You can see the cables on this picture here<ul><li><a href="http://www.wrquattro.com/1981_quattro_difflocks.html">http://www.wrquattro.com/1981_quattro_difflocks.html</a</li></ul>

in that link it shows both vaccum "solenoids" on a single diff with a cable runing to the other diff, is it like that on the 4KQ too? I dont remember a cable runing the length of the driveshaft. Is that showing the rear diff?

You know those ones that guys use when they shave the door handles. They have quite a bit of push/pull power to them, and I've seen them for around $20 each. Should be easy to fab something up using them.

I think that they are showing both systems in place for comparison. You can find the 1980 WR workshop manual at http://www.wrquattro.com/1980WR_manual.html
I can't remember if that has anything in it, it may be that I haven't scanned this stuff in yet.<ul><li><a href="http://www.wrquattro.com/1980WR_manual.html">http://www.wrquattro.com/1980WR_manual.html</a</li></ul>

i think they were from a ford, and it may have been on this forum 4+ years ago. I lurked for a long time before i registered. Anyways, cruise actuators and some clever wiring could easily give you independent electronic control of both diff locks.

I envision the vaccume actuators as a low pressure system, that dosen't put alot of force on the diff lock. As you know the diffs dont engage immediately, they wait untill there is little or no load untill they engage, so I cann't imagine a huge amount of force trying to engage the mechanism, instead a light to medium force with some give to it? Just some hypothetical brainstorming, I have no experience with this system... Does anyone know what the acctual pull/push rating is for the vaccum actuators?

early quattro up until 84 had a bowden cable that ran from the vac solenoid at the rear of the car to the locker on the transmission. I dont know if they were every totally mechanical.

I was told once that the very first Ur-quattros had cables activated by levers between the seats. These may not have ever come to the US though.