I did the swap from drum to disk and have horrible brakes ever since. I changed out the master cylinder and prop valve when I did the swap.
The prop valve was a little different than the one that came on the car, but I didn't think this would be a problem.
The question that I have is if the master for a rear disk set up is the same as the master for a rear drum?
I know that my original master cylinder is good, but will it work with the disks.
Oh yeah, my car is an 86 and the donar car was an 83(if this makes any difference)

 

At the risk of being flamed by al 16,239 members.

The reason the brakes are crappy since yuor conversion to the 1983 rear disc brakes. Is because the pre '89 rear disc brakes suck! Even GM got rid of them.

If you do a search, you will see that much has been written on this subject. Or hopefully one of our members who is more familiar with this subject can enlighten you.

The good thing is, that a lot of people have rebuilt then to work just fine. With no more problems.

Thanx,ANDYZ28

 

So what is the answer to the master cylinder question? I have drums and am switching to disks next week, will I need a new master cylinder? I've been given two different answers lately. What do you guys think? Me and JMDinHawaii would appreciate some info on that. Thank you.

 

Hey guys and welcome to the boards...

If you aren't switching to 1LEs, then you will need a M/C for disc/disc brake cars prior to '89. The 1LEs and '89-up disc/disc cars use the same M/C for a disc/drum (J50) car, but it's different for '88s and earlier.

Andy is right on, it's probably the rear calipers. There was a recall on the rear calipers but it only covered manual shift cars, not autos. Do a search on "caliper recall" or something like that and you should find what you need. Also, look on Daniel Burke's site here:

http://www.ws6transam.org/1LEbrake.html

and he covers what is needed to rebuild the calipers.

Here's a bit from an earlier post of mine and the part numbers you should have:

J50=disc/drum
J65=disc/disc


82-83 M/C

W/J50...................18009127(production)
18013414(service)
W/J65,JE1(Export).......18009126(prod)
18013413(svc)

84-87 M/C

W/J50...................18014286
W/J65,JE1...............18014287

88 M/C

W/J50...................18014286
W/J65, 1LE..............18014286
W/J65(EXC 1LE)..........18014287

89-91 M/C

ALL.....................18014286

Let us know if you have any questions...

Ed, still doing my brakes...

 

He's right you know,The M\C for disc\drum has a piston diameter of 0.945 in and the M\C for disc\disc has a piston diameter of 1 in.

 

Thanks for the help! I understand what you guys are saying about the brakes being horrilbe. I can't hardly believe that GM would even let these cars out the door.
So would you guys say that the stock drum brakes are better than the disk from 82-88? If there is nothing else wrong with my brakes other than a s**ty design then I wish I would have kept the drums. I mean they are really bad. The pedal hits the floor constantly and I can barely stop. There is also a funny howling sound coming from the rear now.
Can someone tell me if there is anything that I can do to make them a little better? I really don't have the money right now to do a complete upgrade.
Thanks again!!

 

I know it would be a pain in the keester, but you COULD put the drum rear back in until you got your disc setup rebuild and functioning properly, that is if you still have the drum rear and didn't just change the brakes.

Ed

 

I originally followed the contemporary advice at the time, and installed the pre-'89 J65 master cylinder. I was very unhappy with the brake performance. So I reinstalled the J50 (drum brake) master cylinder. It made a big improvement in my brakes, it seems the slightly smaller piston diameter (effective area) creates more pressure. I still run this setup everyday.

This follows my "rubber-on-the-road" method of Research & Development work. My next test will be to install a new J50 proporioning vale, and see what happens?

Thanx,ANDYZ28

 

ANDYZ28, I am assuming that you still used the prop valve from the rear disk setup, right? I'm going to put the drum M/C back on this week.
Thanks for the advice!

 

Sorry I reread your post and realized which prop valve you used

 

HEY!!!!!!!!

What am I, chopped liver???????

J/K

Ed

 

Sorry bud, Thanks!!

 

Why not put an adjustible brake proportioning valve in the car? Cause before I had a rear end out of a 87 camaro and it sucked ****. But once I put the adjustible proportioning valve it worked way better.

 

I am wondering the same thing as RevLimit. I have a 91 Trans Am with drums, and am very close to buying a disk rear out of an 87 GTA.
Will I need a new MC out of a pre 89 dick car?
Will I have crappy brakes after I do this conversion?
Will my drum MC perform well with the 87 disk rear?
What do you guys think I should do?
Also, would a post 89 disk rear go into my car with no need for a new MC?

 

I forgot to mention that I am gettind an adjustable prop valve from summitt. Will my drum MC work with pre 89 disk rear if I put this adj. valve in? Thanks

 

Ardels, what's the RPO code for a "pre 89 dick car" anyway?

If you put the '87 disc rear in, then yes you may want a M/C from a pre 89 J65 car. I have one if you want it. However, you would probably be fine with the disc/drum M/C.

You may have crappy brakes if your calipers are messed up and frozen like they tend to do. You could rebuild them with the recall kit and you will be fine.

If you put a post 89 rear in, you will not have to change out the M/C..its the same for all cars 90 and up.

I have no experience with adjustable valves so I can't help ya here.

Check my part number list earlier in the post for which M/C goes with which car.

Ed

 

Okay, I put the J50 M/C back in last night. Now I have absolutely no brakes. I bled the crap out of them with no luck. I think that I am going to buy a new M/C and prop valve.
As far as the adj prop valves....what is the method to adjusting them correctly? Do you need some kind of guage or is it a rubber to road kind of test? I think that it might get a little dangerous to drive if it wasn't adjusted properly.

 

I know someone who try to set his own up and damn near lost the car.He then took it to a garage and have them adjust it on their brake tester.You could test it by yourself and it might be ok but is it worth the risk?

 

ebmiller-a "pre 89 dick car" is a car that is built when you're posting threads on thirdgen.org and you're supposed to be working instead, and you can hear the bossman coming. Anyway, thanks for the info, I appreciate it. One last question:
Will I need a new MC, or anything else, if I install a 87 rear that has the 89-96 style diSks on it, into my 91 Trans Am? Thank you.

 

To the best of my knowledge, you should run a M/C from a '90-up car, GM PN 18014286 and the prop valve for an '89-up car with rear disc brakes, GM PN 10136840.

Look at Daniel Burke's page. He lists part numbers and descriptions for a 1LE swap, but if you read it you'll be able to tell what you need.

Here's his link:

http://www.ws6transam.org/1LEbrake.html


This SHOULD be correct.

HTH....

Ed