i have a 83 Z28 i'm swapping to rear disc brakes, the 82-88 disc proportioning valve is no longer avalible. What is the difference with the 89-92 disc proportioning valve, and can I use it without issue on my 83 with rear discs? i searched through a lot of threads but didn't really find any definate answers.

 

If I am not mistaken the 89-92 propotioning valve is the same for disc and drum brakes. I had drum from the factory and put disc on and didnt change the proporttional valve. So you should be good with the 89-92 one.

 

i have heard that 91/92 is the same disc or drum. I don't understand the theory but this may actually be true. As far as 89+ goes...there was a threading change, along with the fact that when you got rear discs on 89+ cars, i believe they were bigger, like maybe 11.5" discs in the back. Don't quote me, been a while since i've read up on everything.

 

I have a 91 RS, my first axle swap was to an 87 9 bolt with the iron calipers. My car ALWAYS used to pull to the right, I got used to it and drove it like that, wasnt a huge pull or anything anyways. When i swapped in my 4th gen rear i also swapped in a prop valve from a disk/disk car. Cant recall if it was from a 3rd or 4th gen but my car doesnt pull anymore. You should be good if you just go pull one of a Disk/disk car from the JY, you can get one from a 3rd or 4th gen. I have never understood if the prop valves are the same for disk/drum or disk/disk cars between 89-91 but i can tell you i dont have a pull anymore.

 

I know the 92 will work. I put a 4th gen disc rear in my car and had no issues.

 

The '89-92 MASTERS are the same but the props are indeed different, and the differences are internal to the valve. You can't tell just by looking at them. Keep your master and swap the prop if you like, others say you don't have to so you do have an option. I have many new GM prop valves in the shop if you'd like one, I got some while I still could.

Ed

 

i'm swapping in a '98 4th gen rear with the 12" discs, i'm also running a lsi master with the ls1 booster, my mc went bad and i got a free booster/mc from a 2000 so i put them on, basically just for the appearance of the mc as i don't think there is anything else to be gained by it from what i've read. is the 4th gen prop valve compatable with the 3rd gen cars? i didnt see it on the car i took the mc from, the lines went straight to a abs unit. i see year one sells the 89-92 prop valve, and from what you guys are saying on here i shouldnt have any problems using the 89-92 valve? its about a hundred bucks new, ed are yours any cheaper?

 

i'm running 2000 booster, MC, rear axle with the 12" PBR setup. I ended up finding a used 89 prop valve. The threads matched up to the 88 threads i had in my car, i just needed to bend the MC to prop valve lines to maintain the clean aligned look. From what i read back when i did the swap, in mid 89, i believe they changed from metric to SAE fittings, i may be incorrect or backwards. Although it woudln't be terribly hard to cut the tip off, put the correct fitting on, double flare (or bubble, can't remember), and then bend it to where you need it and go from there.

 

alrighti found one at the local yard from an 82 GTA with rear discs. from what i'm aware this should work perfect on my 83, i think 82-83 used SAE fittings and 84 up was metric? the brake resivour was almost empty, but fluid did run out of the prob valve when i removed it so hopefully its not stuck.