I finished installing a posi rear with disc in my 86 z28 which originally had open dif. with drums. The process was fairly easy, even for someone with limited equipment and experience. I did not need a proportional valve for the brake conversion, the front brakes lock first every time and the rear work perfect. One thing I think should be listed on the tech article about the rear swap is the sway bar bushings. Before you start pick up a pair of them, because most likely you will not be able to use the old ones. Pep Boys, auto zone, etc. didn't carry the rear bushings so I bought the ones used on the front sway bar and they work fine and cost less.

The car drives much better. Acceleration has greatly improved and the RPMs on the highway are fine (I have 3.42 gears).

 

A disc and drum brake booster is not the same as a disc/disc booster. Although your setup may work, you really should use a disc/disc booster and master, along with the correct proportioning valve.

 

agree above. I'm glad you're happy, but you really should dial the brakes in with an adjustable proportioning valve. Ideally the rears should lock up just before the fronts.

You're doing good though. I've never had my fronts lock up, though I've had them fade away to nothing a few times.

 

hopefully no ones brakes lock up when they are applied, then we need more than a proportioning valve. also correct me if im wrong, the brakes dont apply one set before the other. more so they both apply at the same time just different pressures. front gets about 70 percent of the brake power while rear gets about 30 percent.
kent

 

Yea you are most likely right, better safe then sorry. Could i just install the proportional valve or do I have to get a new master and booster as well?

 

You're right, the brakes are applied evenly, but the backs should reach lock up pressure first since it takes less pressure to lock the rears...less weight and all. Car manufacturers have built cars this way forever since rear wheel lockup is considered a safer condition than locking up the wheels that steer. Like when the factories set up production cars to understeer at the limit because it's considered a safer condition than oversteering.

Truth is my iroc is the only car I've ever owned that it is practically impossible to get any of the brakes to lock in a panic stop situation. The factory brakes on these cars are very weak regardless of what factory drum/disc disc/disc combination you may have.

Go 100mph and cram on the brakes, they last about 3 seconds and start to let go.

 

you can probably keep your existing master cyl and booster. Get a 40 buck summit adjustable prop valve, install by the directions or get help on this board, then **** with it until all four lock up at about the same time. Let the brakes cool down a bit between tries.

If you went to discs on the back and didn't change anything else, your rears are probably doing next to nothing for you. It takes a lot more pressure to run discs than drums.

 

so did the factory hardline connection on the body of the car connect right up to the 4th gen rear's lines on the rear housing? what kind of rear end did you use? 3 channel or 4 channel? thanks just checkin some information

 

The 4 wheel disc and disc/drum boosters are different. To get the right boost you should use the right one.

 

how is the width ?

i heard the 4th gen rears are wider 2" on both sides

true ?

did you keep the same wheels as you had on the old rear?

 

its alittle less than 2inchs per side... if i recall right, i think mine was overall 3 1/8 to 3 1/4 inch longer...not the best measurement but a good estimate. i have a 98-02 4th gen rear tho which are tad shorter than 93-97's.

 

Real close:

Replacement axles are actually 1-5/8" different for the 2 cars on each side, or 3¼" overall.

 

Is it ok to take the brake booster from a 95 Camaro, if that is where the rear end was taken out of, for disc/disc? Would it fit in a 91 Camaro that original had drums or would an aftermarket booster need to be purchased? That is if the brake booster in the 95 works. Thanks


-Russ

 

Im also going to be swapping in a disk rear in place of my drum rear soon. About the brake booster issue, would I need to go and buy a brake booster for a 4th gen car, or buy one for a 3rd gen that came with 4 wheel disks?

 

I'm not sure that anyone bothers with the master and booster - I didn't on my swap - I did change out the proportioning valve, although I didn't do a before/after comparison to know for a fact whether it made a difference.

The adjustable valves are for those that like to fabricate things - you either have to have every adapter known to mankind, or make your own flared lines to rig one in. I just got a 3rd gen rear disc prop valve and it was a simple 5 minute swap. I haven't tried to lock them up, but I've had no braking issues at all in over a year.

 

On 91/92 cars, a prop valve change is not needed, right? I'm doing mine in a few days. Swapping out the master cyl. with a 91/92 unit may be another option for older cars (assuming no prop valve change).

 

As I understand it...

It has nothing to do with the year of the car, but whether the car had rear discs to begin with. There are two different proportioning valves, one for rear drum, and one for rear disc. They are internally different in that they have different pressure levels depending on the rear brake type. A 1992 with factory rear drums (such as mine) would have a drum proportioning valve, that would need changed to a disc proportioning valve with a rear disc swap.

 

i have heard the drums require more pressure than the discs and if you run the drum proportioning valve, you have a big rear brake bias and have a chance to lock up the rears first before the fronts which is not quite ideal lol

 

hey camaronewbie, would you mind telling me where you got your prop valve? From the donor car or aftermarket? If it was after market did you just use the cheap summit 1 inlet/1 outlet, 1/8 in inlet size? Seems your swap was a success, just trying to get some info for when I do mine in a few weeks but I dont know much about brakes. Luckily my friend will be walking me through the bleeding and such. Thanks


-Russ

 

Genhero

Just walk into a dealer and ask them for a 91 1LE prop. valve, only $65.

 

Easy enough


-Russ

 

Your kidding right?

You don't want the backs locking up before the fronts. If the front brakes lock in a panic situation you lose steering but go straight. If the rears lock first then the car is going to want to spin.