Disc Brake Conversion

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Blake442

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Apr 24, 2007
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That looks like a late '70s WS6 F-body master cylinder (the ones with factory 4-wheel disc's).

We put the same one on a MCSS we converted to 4-wheel disc at work.
 

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86Cutlass383SR

G-Body Guru
Apr 1, 2009
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Sesser, IL
I've spent a few years looking into this swap, myself. The 3rd gen f-body rearend is the same as our g-body cars as far as the brakes go. The "LT1" (93? - 97) rear disc caliper uses the caliper piston to clamp the pads to the rotor for the parking brake. I've heard it's prone to rusting and harder to keep working for this reason. The "LS1" (98 - 2002) rear disc uses an internal drum in the rotor for the parking brake. Better setup. HINT- where do you think *Brand B---* gets their brake parts from? Solution - from PBR Austrailia. The same factory GM gets it's parts from!!!

http://www.thirdgen.org/ls1reardisc

If you want a cheaper big front brake setup you can also do a 13" Vette setup on the g-body spindle with a simple adapter. Stock g-body front disc are 10.5". You can get these adapters from Ed Miller http://www.flynbye.com for $75. He can also modify the combination valve to work with rear disc brakes for about $30. I plan to run an adjustable proportion valve to adjust rear pressure. You then run the stock master cylinder. To run the 13" Vette front brakes you must use a 17" wheel and make sure the wheel clears the caliper. If you don't do the front brake upgrade then you end up with 12" rear disc and 10.5" front. You may end up with the rears locking up first unless you cut the rear pressure way back. Kinda nullifys the effect of the rear disc.
 

Blackboy23

Not-quite-so-new-guy
Aug 17, 2009
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Always near Chicago
Blake442 said:
That looks like a late '70s WS6 F-body master cylinder (the ones with factory 4-wheel disc's).

We put the same one on a MCSS we converted to 4-wheel disc at work.


It seems like what your saying is what he has will work for what I want.. What car does this set up come off what is the WS6 F-body?????
 
Sep 1, 2006
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Tampa Bay Area
Well...no. It is NOT a bolt on to an original drum brake 7.5/7.625 10 bolt rear axle. The flange on a drum brake 7.5 is a weird 3 bolt arrangement that is not shared with any other axle assembly in GM's history. The 8.5 10 bolt (442/GN, etc.) uses a 4 bolt flange that is the same as the disc brake F body and S-10 rear axles use, and the caliper bracket from one of those will bolt to an 8.5. All is not lost, but you will have to do some fabrication to make the brakes and 7.5 axle live together in peace and harmony. What kind of fabrication I am not sure just yet as this is on my list of future mods for my car-if I can't find an 8.5 first.
 

Blake442

Geezer
Apr 24, 2007
6,864
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Minneapolis
Blackboy23 said:
Blake442 said:
That looks like a late '70s WS6 F-body master cylinder (the ones with factory 4-wheel disc's).

We put the same one on a MCSS we converted to 4-wheel disc at work.


It seems like what your saying is what he has will work for what I want.. What car does this set up come off what is the WS6 F-body?????

WS6= option package that featured 4 wheel discs.

Go order a master cylinder for a '79 Trans Am with the WS6 package at your favorite parts store, and make sure they know it's for a 4-wheel disc car.
 

86Cutlass383SR

G-Body Guru
Apr 1, 2009
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Sesser, IL
85 Cutlass Brougham see the thirdgen link I posted above. Tells ya how to mod the 7.5 to bolt on the LS1 rear disc.
 
Sep 1, 2006
6,687
33
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Tampa Bay Area
86Cutlass383SR said:
85 Cutlass Brougham see the thirdgen link I posted above. Tells ya how to mod the 7.5 to bolt on the LS1 rear disc.

The comment was not directed at you, it was meant as a clarification to the OP. I will check the link though, but I will probably run LT1 brakes when I do my car. They are available to me cheap at the local U Pull It yard as they were an option on some V6 cars that show up there on occasion. However, I will keep my eyes open for any newer S trucks or Camaros that may have those brakes too. I am still planning my cheapskate brake upgrade and suspension geometry correction right now, so I am open to ideas.
 

86Cutlass383SR

G-Body Guru
Apr 1, 2009
720
6
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Sesser, IL
No problem, I knew you weren't directing it at me. :wink: I just wanted you to know your options. I haven't done the swap myself but other say the LS1 brake, particularly the e-brake, is so much better.

I'm sending you a PM.
 

uneek1976

G-Body Guru
Jul 24, 2009
653
129
43
Sugar Grove IL/ Chicago
I just finished doing a rear disc conversion on my regal using calipers and rotors from a c5 corvette. Tha parts that i changed was the master, thats from a 84 caddy edlo, disc-disc preportional valve, and caliper mounting brackets that was ordered from Ed Miller.
 

86Cutlass383SR

G-Body Guru
Apr 1, 2009
720
6
0
Sesser, IL
I knew Ed was proto-typing a setup for our cars but has he got the e-brake issue solved? Last I talked to him he was still working on it.
 
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