Rear disc brakes for a GM 10 bolt 8.5, True-false or maybe ?

I have had to change the prop valve to a 4 square equal pressure valve. I used the 4 wheel drum one on the last car and it worked perfect. If the car has disc already the valve will hold back pressure to the rear ad it will not give you the stopping power. I just did this to a GTO recently that was struggling with no rear braking power. (he had installed the rear disc from a kit but forgot to change the pressures) As for the TA rear discs I have not officially done this other than to bolt it to the rear end. I am not aware of what it takes to make the Ebrake work on the TA stuff....yet......

 

couple places sell the bracket to do such thing usualy like 50-100 bucks
I can also say a stock disc/drum valve is a no go..it either didnt give it enough pressure or eventually have calibers hang up for miles and cause massive heat

 

while my rear is out, it would be cool to do this swap so long as the price stays down and the major fabrication stays easy = no welding tubes etc,. Bolt on, bleed, then go.

 

I picked up 78 Firebird Formula, haven't decided what to do with it yet. It has front discs and a much larger front sway bar than my 70 drum equipped Skylark. It is currently buried in 3ft of snow, so I cannot check on rear disc brakes or rear swaybar. Assuming it has both, can anyone tell me if any of the brake components or swaybars from the Bird will be usable on my 70 Skylark? The Skylark has a 71 8.5 10 bolt going under it from a board members 71 Lark. TY JIM/Rott

 

the brakes don't know if they are on an 8.2 or an 8.5 so they will work. The front sway bar will bolt up using the Bird hardware the rear sway is different

 

Thanks for the reply Mike, appreciated. If this Pontiac was all original, it would stay together as it is a Formula 400-unfortunately the motor and trans are not original, so I am leaning to parting it out, especially if I can put discs on all four corners of my 70 Lark. To further clarify, the 78 Firebird front spindles and rotors/calipers will work on my 70 Lark? And the rear backing plates ,rotors and calipers will work on my 8.5 rear as well? Will I need anything else for the swap? Sorry for all the questions Mike, just trying to make a knowledgeable decision. TY JIM/ Rott

 

The swaybar is about the only thing on the front of an F-body that will directly interchange. You will not be able to bolt up the front brakes and spindles. It will require different (aftermarket, not on the F-body or A-body) upper control arms and aftermarket ball joints specific for the purpose. Research "Tall Spindle Swap" for more info on what you might do or not do. You will also have to have different outer tie rod ends. I'd skip the front brakes and sell them on craigslist. Then you will have enough to make a dent in a factory style front disc kit. You can probably use the brake booster and maybe the brake proportioning valve but those things are cheap if they are questionable at all.

Your rear disc setup will most likely work though I had issues with factory Buick 15" chrome wheels. Calipers rubbed the wheel and had to run a 3mm spacer. You may also have to take a little off the outside diameter of the axles as the rear discs are not as big as drums on the inside. It is a pretty straightforward swap as these things go.

As for other parts, the power steering gearbox and the relief spring in the power steering pump might be of value if it was the W6, which having rear discs ups the possibility. If it is a W6, it will have a close ration steering gear. Some say it has internal stops that limit your turning radius but they can be removed by a competent shop that deals with steering gear, like Lee's Manufacturing. It will require a different rag joint. I'm not sure if 78 had gone to o-ring hoses yet or still used inverted flare.

That's just an overview, not a cookbook for the swaps. Hope that helps clear up a few things.

 

I read over at Pro-touring that you can use the S-10 rear disc set up. You use everything from the backing plate out. You use your original axles, just the S-10 back plate, caliper mount, caliper, parking brake assy, and brake disc. pretty much straight forward install.

Tim

 

Do you have a link?

 

Thanks for all the information, Knuckle busted. Definitely helped with my decision, as to what to do with the Pontiac. I'll flip it and buy aftermarket front discs and hit the junkyard for S10 Rear discs parts. TY Jim/Rott
PS: Be nice to have a write up with pics from someone who has completed the S10 rear disc swap. Hint hint.........

 

What about a kit like this? I would assume it would need a different master cylinder and proportioning valve than the stock power F/disc - R/drum I already have.

http://www.jegs.com/i/Right-Stuff/965/AFXRD01/10002/-1?parentProductId=

 

That is the kit I put on my '71 GS. Works well and mounts up without major issues. You will need the conversion proportioning valve. If you run headers, I recommend getting a kit from Pirate Jack in Asheville NC to mount the prop valve under the master cylinder. I encountered a problem with mine where the headers would heat the prop valve mounted on the frame in the stock location causing the fluid to expand and drag the rear brakes.

 

That looks exactly what I've got on my 70 with an 8.5 rear. I don't have backing plates which is a nice extra in that kit. It works well. Just be aware of a possible interference with factory chrome Buick wheels.

 

Did any one ever do the s-10 rear disc conversation, and how did it come out ?

 

Ok guys, update time. "200 4R trans done crapped out, still works but feels like crap. trans shop says 3-4 weeks before they can get it, in for a rebuild. Figure while just sitting in garage I do a few projects I been putting off. Removed old rear drums, and installed rear disc package from a 96 blazer($40). New ceramic brake pads ($40), summit crossed drilled rotors ($100) and calipers ($60) from summit. And, I have to say it looks great and all came to gather very easy, and what a difference it makes, took around the block test ride, and almost went through the windshield a few times, "What a difference" !!

 

Pics...

 

Did you use the Blazer caliper brackets?Were you able to retain the emergency brakes?Any mods needed to the axle housing?What about backing plates,Blazer?

 

Looks good. Does it work with 15" Buick wheels?

 

the blazer caliper brackets are the main part and has to be used, will have to get new emergency brake lines, No mods needed to axle house, "Both axle houses are 10 bolt, 8.5...

 

Not sure but doubt it, was previously told for 17 and up