soarestransam

Ok so I got a 88 Gta with the non performance brake package I have a 89 Gta 9 bolt with the pbr brakes I was looking into swapping it all out put the 89 rear in my 88 do I have to change anything over to make the 89 pbr work

JamesC

iTrader: (5)

The swap itself is direct. You'll need the first design 1LE combination valve (or an adjustable), first-design parking brake cables, which are 1434 mm, and the correct drive and/or driven gears for the speedo to read correct (providing the new rear as a different ratio).

The 9- and 10-bolt braking systems are identical (with the exception of the backing plates), so the following link will provide pics and part numbers:

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

JamesC

soarestransam

Ok so I got the 88 9 bolt out today an cleaned up the 89 pbr rear end. I'll paint it tomorrow an get ready on the install of it so what proportional valve do I need exactly. should I just get one from autozone with the performance package with disc brakes??? also I checked there today to get new e brake cables an they are not available there, what auto parts stores will carry them for a 89 gta rear end with the performance package ???

Gumby

check online first, last time I asked about a prop valve they said its a dealer only item.

JamesC

iTrader: (5)

http://www.flynbye.com/catalog/i40.html

Check the link in post #2 for various parking brake cable part numbers.

JamesC

soarestransam

Ok so I gotta get the first design master clyinder for drum brakes anything 84-92 for the proportional valve I'm just gonna ask for one at autozone with the proformance package with disc brakes

JamesC

iTrader: (5)

While the 1LE system calls for a drum master, it's probably not needed. That said, I used one on my conversion).

https://www.thirdgen.org/forums/susp...fferences.html

The disc combination valve, 82-88, is designed for cars equipped with the Delco-Moraine system (10.5" rotors and iron calipers), the 89-92 for cars with PBR's (11.7" rotors and alum calipers). Of the latter, there are two designs, one for mid-89 down with M1.0 tube nut threads and one for mid-89 up with M1.5 tube nut threads. That you'd be able to purchase the valves at an auto parts store is unlikely.

JamesC

soarestransam

Ok so I found this master cylinder http://www.autozone.com/autozone/par...7_56045_0_7735, is this the right drum master clyinder I will need to make this work for the proportional valve looks like I'll just order that one from flyinbyperfomance.

JamesC

iTrader: (5)

If the drum master fits your 88, you should be good to go.

JamesC

soarestransam

Ok sounds good I'll bring my lines to see if they thread in no prob am then I just gotta find a proportional valve for the 1le

ZF6camaroZZ4

If you have standard 4 wheel disc, 10" ones front and rear. You can install the pbr's out back "without changing anything else". You will love the braking balance.
Now if you put the pbr's out front, then you need to change master/prop.

JamesC

iTrader: (5)

Personally, I'd prefer using the combination valve designed for a specific braking system: There are different valves for disc/drum, for disc/disc, and for disc/1LE. Each apparently with a different bias.

The proportioning section of the combination valve is usually used in the rear brake line.

JamesC

soarestransam

Then why is everyone telling me that I have to change the prop valve, an master if I keep the set up I have now will it give me a soft long travel pedal ???

Sojer

My car is a swaped from 87 2.73 drum posi to 3.27 disk posi brakes fine but I will change when I do the ls1 brake swap, I gave the calipers painted just need to mod the other stuff

InfernalVortex

iTrader: (4)

I swear I remember reading somewhere that all the 89+ 4 wheel disc cars used the same prop valve, which was the 1LE valve. Which makes sense, because the proportioning valve always sends 100 percent of the line pressure to the fronts, and its main job is to just limit the amount of pressure that goes to the back (which you have corroborated), hence the "spring mod" people do. And in that case, the 1LE cars used the same rear brakes that the non 1LE cars did, so using separate prop valves would be pointless. But that may or may not be correct, you know how things you hear on the internet turn out...

JamesC

iTrader: (5)

The following from my Parts and Illustration Cat.:

89-91 shows the same Cylinder, Brk Master GM 18014286. Earlier years show different masters for J50 and J65. GM, however, pretty much made them interchangeable:

https://www.thirdgen.org/forums/susp...fferences.html

There are different combination valves (if only one was needed, why would GM design valves for different applications?). For exampe:

Valve, Brk Combo (1989 2nd Des) (J50) (1990 [and also 91]) (J41, J42) GM 10136839
J41 - BRAKE SYSTEM, POWER, FRONT DISK, REAR DRUM, CAST IRON
J42 - BRAKE SYSTEM, POWER, FRONT DISK, REAR DRUM, ALUMINUM

Valve, Brk Combo (1989 1st Des) (J65, 1LE, Y82) GM 14089496
J65- BRAKE SYSTEM, POWER, FRONT & REAR DISK
1LE - PERFORMANCE PACKAGE, SHOWROOM STOCK RACING
Y82 - MERCHANDISED PACKAGE, FORMULA

JamesC

soarestransam

Ok so what I'm gonna do is try it with the master an prop valve I have now an see how the pedal will be if it isn't to my liking then I'll just order all the stuff for the 89 set up I'm trying to redo this car on a budget

JamesC

iTrader: (5)

The disc/drum and disc/disc valve will stop the car (but I'm uncertain of how well or efficiently). To be truly assured of the best performance from 1LE brakes, the best choice would be 1LE components designed for that system.

You might also peruse the following link, which details both the front and rear 1LE swap with pics and part numbers:

http://web.archive.org/web/200605221...e.html#1LErear

Best of luck on your project.

JamesC

Gumby

do believe the problem comes as the prop valve for rear drums is designed to keep or hold several PSI [ I think its 7-9] of pressure in the rear lines so the drums work proper, been that way on GMs for a long time. As drums take longer to react if not. One might notice a bit of drag in the rear with rear disc and/or shorter pad life with a disc/drum prop.

cheapest solution is hit ebay for a "hotrod" brass prop valve of your liking, [disc/disc, disc/drum] it will use standard thread fittings and is easy to cut off the metric end and reflare them.

Its what I did and now the only places I have metric ends is where it screws into the MC and in the rear. but plan to change the rear parts for standard ends next time around.
[hate those double flare import metric line, I have a GM not a toyota]

ZF6camaroZZ4

I dont know why people would tell you that. If they had ever done just the pbr swap on a 10" brake system, they wouldnt.
They also wouldnt tell you you need the 1le prop valve for sure, thats for full 1le brake system front and rear.
We did this pbr swap on my car, and my brothers. All we changed was the rear end/brakes. < and the brakes worked awesome!

Once the vette brakes went out front, do you/we needed to changes other stuff.

I remember that stuff on the residual psi, that was done in the master. Something about drums move to fast and would let air in the system. Probably why when they list all the 1le stuff, theres a secondary valve listed.. thats the second valve in the master.

JamesC

iTrader: (5)

People don't normally swap out the combination valve for a front only brake change. It's only the rear that requires proportioning (either with the correct valve or an adjustable). Note that Ed Miller, for example, doesn't sell a 1LE valve with his front set-up, but one is included in his rear set-up. He describes the valve as a "GM factory 1LE/J65 rear disc brake proportioning/combination valve."

http://www.flynbye.com/catalog/i40.html

There are only two 1LE valves. Except for the difference in tube nut threads they're the same.

JamesC