I have an opportunity to buy a disc brake rear for next to nothing. Other than changing the proportioning valve what else can I expect to change to make the swap? Will the parking brake cables work or are they a differrent set up?

 

Hi there. I'm looking into this too. I can also guess that this is one of the most frequently asked questions on this particular board. Here's what I know.

Your going to need a new proportioning valve (like you mentioned) and from what I've seen, you may have some difficulty working the emergency brake (another thing you've noted). You might want to take this opportunity to replace all the bushings and bolts holding the rearend on but outside of that (and maybe a speedo gear in the tranny if you are chaging gears) there shouldn't be any other surprises.

Hope this helps,

 

::bounces face off desk:: It will work without the proportioning valve. Its not mandatory its just better. Its not like your gonna put the rear in without the new valve and the rear brakes are not gonna work.

 

"Best" is always better. Besides, I recently picked up a prop valve and a master cylinder for 20 bucks off a certain auction site. It arrived in great shape.

Now I just have to find the rear end to go with it.

 

I switched prop valves a while after I put the rear in and there was absolutely no change in braking.

 

now my ? is i have an 85 camaro that had discs now it has a 95 rear with drum can i tear off my disc brakes and put them on the newer rear end

 

Where is the crow I can eat?

 

WTF??

If you're trying to put disc brakes on a drum rear you will need to turn the axle flange's outer diameter down. The drum axles are bigger and the rotors wont go on without turning them down.

 

What do they measure out to?

Personally, I don't understand why the hub would be different as the wheel is supposed to be a snug fit over the hub. I guess the difference is within a few thou eh? I'm gonna measure mine today vs the few sets of drum axles I have.

I'm also surprised folks have said not to switch the prop valve. I verrified when doing my swap the masters are the same part # between all the late 80s/early 90s but the prop valve for disk is a different #, which leads me to believe that the specs are infact different. And although some people didnt "feel" or "notice" a difference, i'm sure there is infact a difference in stopping distance and or pedal effort. GM doesn't go out of their way to to increase costs, so their is an obvious reason for the change.. Too many hacks on this site. The last thing you want to function worse than factory is your brakes..


-- Joe

 

it wasn't a snug fit, they wouldn't go on at all. Hub diameter on the drum axle measured 6.0", hub diamerter on the disc axle measured 5.850" and the ID of the brake rotor was 5.900".

 

Oh thats the problem. I thought you guys were talking about the actual hub the wheel/drum rides on.. Hrmm.. interesting.. I wonder why..

-- Joe

 

I wondered the same thing. Doesn't make much sense to me why they'd use two diffent axles but you know GM I had never heard anyone mention the problem either and was unaware of it until I went to slip the rotors on.

 

I had to turn my axle flanges down to fit the roters on a drum rear. it was no big deel 5 min on the lathe. eny machine shop can do it for you. buy the way my car WOULD NOT LOCK up the rear tires on a gravel road untill I changed the proportioning valve.

 

My PBR's won't lock up until the pedal is at the floor. I tested this today with my sister in the car on the lift. (after bleeding them for about 2 hours).. They just suck, even with the right proportioning valve. wtf.

-- Joe

 

Did you shim so that the caliper was centered over the rotor? And if your parking brake doesn't work, did you adjust "free travel"?

https://www.thirdgen.org/forums/faq-...iscs-89-a.html

JamesC