Hey,
My 89 GTA's rear brakes won't lock up when in gear, even with the rear end jacked up. I bleed the rears just to see if that was it, but no difference.
I've also noticed that it takes more brake pedal pressure to stop this car than is does my 86 Z with drum rears.
Something is screwy here. Where should I look first? The break light isn't on or anything like that, and there doesn't seem to be any leaks.
Could it be the master cylinder? Metering block? Proportioning valve? Calipers?
The rear is a BW 3.27, and has rear discs (GTA, eh).
Thanks
Jeremy

 

Sounds like the piston in the calipers may be frozen. I had the same problem with my 89 GTA, same rear end. When i swapped the rear to a 4th gen w/ a taller gear, I managed to get the disks and rear calipers never had the problem again. I have heard that it is commen for our cars. Go figure

 

I have the same trouble with 89 Iroc. When I had it dynoed and smogged they were unable to keep the rear wheels from turning with the brake fully applied while the car was in 'Drive'. I have talked to others with the same problem but nobody has been able to isolate the trouble.

 

What everyone claims is that the problem lies in the prop valve. Many (??) disc/disc f-bodies came with disc/drum prop valves. Alot of people here have had great success w/ replacing the prop valve with either aftrmkt or stock disc/disc one. This topic has come up alot...you might find more info in a search.

 

RednGold86Z, what year were the disks brakes? (You said the axle's from a GTA?) If they're 82-88, those calipers were recalled by GM. You'll need the recall kit, more info here: https://www.thirdgen.org/techbb2/sho...threadid=78725

Try this, too. Hit the brakes, then release the brake pedal quickly, then quickly press the brake pedal again. If the car stops perfectly after the second-quick-press, then you need to put the recall kit in. That's what was happening with my '84 3.73/posi/disc axle I swapped into my '86... went away after I put the recall kit in.

 

Thanks Tom. Unforunately I have an 89 so apparently the fix isn't as easy for me.

Who makes a good aftermarket proportioning valve?

 

Now we're getting somewhere. Other than what Tom mentioned this is the first bit of information that may help get my problem fixed since it's an 89 and was not affected by the recall. Many have suggested the prop. valve but I was unaware that some were that way from the factory.

 

I had same problem on my 87 and its a very easy fix,
Take off that bleeder on front of prop valve, behind there is a piston/valve that with an 0 ring on it..
Remove that valve but you will need to block the bleeder hole now. That allows alot more fluid to go to the rear brakes.
Worked perfect on mine, under extreme braking in get some chirping of rear tires.
It was discussed here before and is a common mod. Try it out,If you don't like puy it back in.