if anyone knows where i could come by a new or used perportioning valve for an 85 gti? i need to figure something out soon, im cruising around with ONLY front brakes, no rears.
i would go for a known good used one, or a brand new one if someone could find one. the parts stores around here said they are NLA..
The Worldpac guys carry them, although on the 85 they show as the kind that attaches to the master cylinder rather than the under-the-car version:
Honkin big link
well, my car definitely has one under the car.. operated by the rear axle.
Are you running stock brakes on the front? When I did the conversion on the caddy I eventually eliminated the prop-valve altogether. I wet the street down in front of my house, doing a wet braking test, the fronts locked up first. It might be different in the snow.

Do the test and see what happens.
Cheers,
-JB
I realize that this is sort of a hijack, but shouldn't you test brake bias in the dry? The way I see it, the more traction you have, the more you are able to unweight the rears, at which point the bias comes into play. It would follow (assuming that I'm not out in left field so far) that as it got wet or icy the bias would move towards the fronts, I think this is why vw moved to the dynamic proportioning valve. Actually pretty neat how those work inside.
As best I could tell, the dynamic one I took off when I replaced the drums with disks did not have check valves in it, only the prop mechanism. I thought all drum setups had check valves, but this did not seem to. Maybe the self adjusters keep things tight enough that the checks are unneccesary? Given the number of people who say that they run without them, I'm surprised that you say your rears are not working.
What I linked I know drum brake cars use. I don't know about the disc brake cars though.
i live in the pacific north west. it rains all the time. i would rather do a wet test.
I do it on a gravel road south of town,
my brake adjustment test track.
Pretty easy to see when they locked up.